Document:

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                                                                   EXHIBIT 10.37

                        FOUNDER STOCK PURCHASE AGREEMENT

     This Founder Stock Purchase Agreement is dated as of the tenth day of June
1998 (the "Effective Date") by and between MachOne Communications, Inc., a
California corporation (the "Company"), and Kevin Grundy ("Founder").

                                  WITNESSETH:

     WHEREAS, Founder is a founder and a key employee of the Company.

     WHEREAS, the Company desires to issue and the Founder desires to acquire
stock of the Company as herein described, on the terms and conditions
hereinafter set forth.

     NOW, THEREFORE, IT IS AGREED between the parties as follows:

     1.   Number of Shares and Price Per Share. The Founder hereby agrees to
purchase from the Company and the Company agrees to sell to the Founder eight
hundred thousand shares of the Company's Common Stock (the "Stock") with a fair
market value of $8,000 (or $0.01 per share). The consideration for the Stock
(the "Purchase Price") will be paid by Founder in cash, by check, or promissory
note concurrent with the execution of this Agreement against the Company's
delivery of a stock certificate evidencing the Stock.

     2.   Unvested Share Repurchase Option. The Company shall have the option
(the "Unvested Share Repurchase Option") to reacquire any shares purchased
pursuant to this Agreement which have not vested in the Founder pursuant to
subsection 2(a) (the "Unvested Shares") under the terms set forth in this
Section 2.

          (a)  Vesting of Shares. Founder shall purchase the Stock effective
upon the date first written above, but the "Initial Vesting Date" for
determination of vesting of the Stock shall be December 3, 1997. The shares of
Stock purchased by the Founder will vest (the "Vested Shares") on and after the
Initial Vesting Date in accordance with the following formula:

<TABLE>
<CAPTION>
     Date                                    Number of Shares Vested
     ----                                    -----------------------
     <S>                                     <C>
     On the Initial Vesting Date             116,664 shares of Stock will
                                             vest (14.583%)

     For each full month of the Company's    An additional 2.0833% of the
     continuous employment of Founder        Stock will vest (16,664 shares)
     following the Initial Vesting Date      for each full month of service.
</TABLE>

     Provided that the aggregate number of shares of Stock constituting Vested
Shares may not exceed 800,000 shares (as adjusted for stock splits and the
like). In the event a fraction of a share is vested, the number of vested
shares shall be rounded to the nearest whole number.

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<PAGE>   2
          (b)  Exercise of Unvested Share Repurchase Option. If the Founder's
employment with the Company is terminated for any reason, with or without
cause, voluntarily or involuntarily, including termination due to death or
disability (as defined below), or if the Founder or the Founder's legal
representative attempts to dispose of any Unvested Shares other than as allowed
in this Agreement, the Company may exercise the Unvested Share Repurchase
Option by written notice to the Escrow Agent (as defined in Section 8) and to
the Founder or the Founder's legal representative within 60 days after such
termination or after the Company has received notice of the attempted
disposition.

          (c)  Payment for Shares and Return of Shares. Payment by the Company
to the Escrow Agent on behalf of the Founder or the Founder's legal
representative shall be made in cash within 60 days after the date of the
mailing of the written notice of exercise of the Unvested Share Repurchase
Option. For purposes of the foregoing, cancellation of any promissory note of
the Founder to the Company shall be treated as payment to the Founder in cash
to the extent of the unpaid principal and any accrued interest canceled. The
purchase price per share being purchased by the Company pursuant to the
Unvested Share Repurchase Option shall be $0.001 per share, adjusted
appropriately to reflect any stock split, stock dividend, recapitalization,
etc. Within 30 days after payment by the Company, the Escrow Agent shall give
the shares which the Company has purchased to the Company and shall give the
payment received from the Company to the Founder.

          (d)  Early Termination of Unvested Shares Repurchase Option. The
other provisions of Section 2 notwithstanding, upon any Transfer of Control (as
defined below), the Unvested Share Repurchase Option shall terminate as of a
date prior to the Transfer of Control, as the Board so determines pursuant to
the definition below, or if no such determination is made, two days prior to
the closing of the transaction involving the Transfer of Control. Any such
termination that was permissible solely by reason of this subsection 2(d) shall
be conditioned upon the consummation of the Transfer of Control. For purposes
of this subsection 2(d), a Transfer of Control shall be deemed to have occurred
upon any of the following events: (i) the direct or indirect sale or exchange
by the shareholders of the Company of all or substantially all of the stock of
the Company where the shareholders of the Company before such sale or exchange
do not retain, directly or indirectly, at least a majority of the beneficial
interest in the voting stock of the Company; (ii) a merger in which the
shareholders of the Company before the merger do not retain, directly or
indirectly, at least a majority of the beneficial interest in the voting stock
of the Company; or (iii) the sale, exchange, or transfer of all or
substantially all of the Company's assets (other than a sale, exchange, or
transfer to one or more corporations where the shareholders of the Company
before such sale, exchange, or transfer retain, directly or indirectly, at least
a majority of the beneficial interest in the voting stock of the corporation(s)
to which the assets were transferred).

     For the purposes of early termination of the unvested share repurchase
option, a Transfer of Control shall be deemed to have occurred only if one of
the events described in the paragraph above has occurred and, within one year
of such event: (i) there is a decrease in Founder's base salary, benefits
and/or bonus compensation; (ii) there is a material breach by Company (or its
successor or assign) of this Agreement or of Founder's Employment Agreement

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<PAGE>   3
with the Company; (iv) the Company fails to obtain the assumption of this
Assignment and the Employment Agreement by MachOne's successor or assign.

          (e)  Transfers Not Subject to the Unvested Share Repurchase Option.
The Unvested Share Repurchase Option shall not apply to a transfer of shares of
the Stock to the Founder's ancestors, descendants or spouse or to a trustee for
their benefit or the benefit of the Founder, provided that such transferee shall
agree in writing (in a form satisfactory to the Company) to take the shares of
the Stock subject to all the terms and conditions of this Section 2.

          (f)  Assignment of Unvested Share Repurchase Option. The Company may
assign the Unvested Share Repurchase Option to one or more persons, who shall
have the right to exercise the Unvested Shares Repurchase Option in his or her
own name for his or her own account.

          (g)  Waiver of Other Option. Founder acknowledges that the Company
has agreed to issue to Founder options to purchase 70,000 shares of its common
stock. Founder relinquishes and waives all right to such issuance or such
options.

     3.   Right of First Refusal. Before any shares of the Stock registered in
the name of Founder may be sold or transferred (including transfer by operation
of law), such shares shall first be offered to the Company, which will have the
right to purchase all or any part of such shares proposed to be transferred
("Right of First Refusal"), in the following manner:

          (a)  Transfer Notice. The Founder or his or her legal representative
shall first give written notice (the "Transfer Notice") of any proposed
transfer to the Company. The Transfer Notice shall name the proposed
transferee, state the number of shares of Stock to be transferred, the price
per share and all other terms of the offer. The Transfer Notice shall be signed
by the Founder or his or her representative and the prospective transferee and
must constitute a binding agreement for the transfer of the Stock subject only
to the Right of First Refusal.

          (b)  Bona Fide Determination. Within 30 days of delivery of the
Transfer Notice, the Company's Board of Directors shall determine the bona fide
nature of the proposed transfer and give the Founder written notice of its
determination. If the proposed transfer is deemed to be bona fide, the
remaining subsections of this section shall apply to the sale. If the proposed
transfer is deemed not to be bona fide, the Founder will be responsible for
providing additional information to the Board to show the bona fide nature of
the proposed transfer and no Stock will be transferred on the books of the
Company until the Board has approved the proposed transfer as bona fide.

          (c)  Failure to Exercise; Exercise. If the Company elects not to or
fails to exercise in full the Right of First Refusal within 30 days from the
later of the date the Transfer Notice is delivered to the Company or 30 days
after the date the transfer is determined to be bona fide (if the Founder is
required to provide additional information as provided in Section 3(b)), the
Founder may, by the later of 60 days after the delivery of the Transfer Notice
to the Company or 30 days after the date the transfer is determined to be bona
fide (if the Founder is required to provide additional information as provided
in Section 3(b)), conclude a transfer of the shares of

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<PAGE>   4
Stock subject to the Transfer Notice which have not been purchased by the
Company pursuant to exercise of the Right of First Refusal on the terms and
conditions described in the Transfer Notice. Any proposed transfer on terms and
conditions different from those described in the Transfer Notice, as well as any
subsequent proposed transfer by the Founder, shall again be subject to the Right
of First Refusal and shall require compliance by the Founder with the procedure
described in this Section 3. If the Company exercises the Right of First
Refusal, the parties shall consummate the sale of shares of Stock on the terms
set forth in the Transfer Notice by the later of 60 days after the delivery of
the Transfer Notice to the Company or 30 days after the date the transfer is
determined to be bona fide (if the Purchaser is required to provide additional
information as provided in Section 3(b)); provided, however, in the event the
Transfer Notice provides for the payment for the shares of Stock other than in
cash, the Company shall have the option of paying for the shares of Stock by
the discounted cash equivalent of the consideration described in the Transfer
Notice as reasonably determined by the Company.

          (d)  Condition to Transfer. All transferees of shares of Stock or any
interest therein other than the Company shall be required as a condition of
such transfer to agree in writing (in a form satisfactory to the Company) that
they will receive and hold such shares of Stock or interests subject to the
provisions of this Agreement, including the Right of First Refusal.

          (e)  Assignment of Right of First Refusal. The Company may assign the
Right of First Refusal to one or more persons, who shall have the right to
exercise the Right of First Refusal in his or her own name for his or her own
account.

          (f)  Termination. The Right of First Refusal will terminate upon the
closing of a firm commitment underwritten public offering to the public of the
Company's Common Stock pursuant to a registration statement under the
Securities Act of 1933, as amended (the "IPO").

          (g)  Transfer Not Subject to Right of First Refusal. The Right of
First Refusal shall not apply to a transfer of shares of the Stock to the
Founder's ancestors, descendants or spouse or to a trustee for their benefit or
the benefit of the Founder, provided that such transferee shall agree in
writing (in a form satisfactory to the Company) to take the shares of Stock
subject to all the terms and conditions of this Section 3.

     4.   Piggyback Registration Rights.

          (a)  If the Company shall determine to register any of its securities
either for its own account or the account of a shareholder(s) exercising demand
registration rights, other than a registration relating solely to employee
benefit plans, or a registration relating solely to a transaction pursuant to
Rule 145 promulgated under the Securities Act of 1933, or a registration on any
registration form which does not permit secondary sales or does not include
substantially the same information as would be required to be included in a
registration statement covering the sale of the Stock, the Company will
promptly give to the Founder written notice thereof and include in such
registration (and any related qualification under blue sky laws), and in any
underwriting involved therein, the number of Vested Shares specified in a
written request made by the Founder within fifteen (15) days after receipt of
such written notice from the Company, except as set forth in Section 4(b) below.

                                       4

<PAGE>   5
          (b)  If the registration of which the Company gives notice is for a
registered public offering involving an underwriting, the right of any Founder
to registration shall be conditioned upon the Founder's participation in such
underwriting and the inclusion of such Founder's Stock in the underwriting
pursuant to an underwriting agreement in customary form with the underwriter or
underwriters selected by the Company. Notwithstanding any other provision of
this Section, if the underwriter reasonably determines that marketing factors
require a limitation on the number of shares to be underwritten the underwriter
may exclude some or all of the Stock with the number of shares that may be
included in the registration and underwriting being allocated among the Founder
and all other shareholders entitled to have securities included in such
registration in proportion, as nearly as practicable, to the respective amounts
of securities which they had requested to be included in such registration
(provided, however, that if the registration is for the account of shareholders
exercising demand registration rights, the number of shares that may be
included by the Founder shall be cut back entirely before any limitation on the
number of shares that may be included by such shareholders).

          (c)  All expenses of the registration shall be borne by the Company,
except underwriting discounts and selling commissions applicable to the sale
of any of Founder's Stock and any other securities of the Company being sold in
the same registration by other shareholders, which shall be borne by the
Founder and such other shareholders pro rata on the basis of the number of
their shares registered.

     5.   Stock Dividends, etc.  If, from time to time, there is any stock
dividend, stock split or other change in the character or amount of any of the
outstanding stock of the Company, then in such event any and all new
substituted or additional securities to which Founder is entitled by reason of
Founder's ownership of Unvested Shares or Stock shall be immediately subject to
the Unvested Share Repurchase Option or the Right of First Refusal,
respectively, with the same force and effect as the Unvested Shares or Stock.

     6.   Consent of Spouse.  If the Founder is married on the date of this
Agreement, the Founder's spouse shall execute a Consent of Spouse in the form
of Exhibit A hereto, effective on the date hereof. Such consent shall not be
deemed to confer or convey to the spouse any rights in the Stock that do not
otherwise exist by operation of law or the agreement of the parties. If the
Founder should marry or remarry subsequent to the date of this Agreement, the
Founder shall within thirty (30) days thereafter obtain his or her new spouse's
acknowledgment of and consent to the existence and binding effect of all
restrictions contained in this Agreement by signing an additional Consent of
Spouse in the form of Exhibit A.

     7.   Legends.  All certificates representing any shares of Stock subject
to the provisions of this Agreement shall have endorsed thereon the following
legends:

          (a)  "THE SHARES REPRESENTED BY THIS CERTIFICATE ARE SUBJECT TO A
REPURCHASE OPTION AND RIGHT OF FIRST REFUSAL IN FAVOR OF THE COMPANY OR ITS
ASSIGNEE SET FORTH IN AN AGREEMENT BETWEEN THE COMPANY AND THE REGISTERED
HOLDER, OR HIS OR HER PREDECESSOR IN INTEREST, A COPY OF WHICH IS ON FILE AT
THE PRINCIPAL OFFICE OF THIS COMPANY.

                                       5
<PAGE>   6
          (b)  "THE SECURITIES EVIDENCED BY THIS CERTIFICATE HAVE NOT BEEN
REGISTERED UNDER THE SECURITIES ACT OF 1933, AS AMENDED, AND MAY NOT BE SOLD,
TRANSFERRED, ASSIGNED OR HYPOTHECATED UNLESS THERE IS AN EFFECTIVE REGISTRATION
STATEMENT UNDER SUCH ACT COVERING SUCH SECURITIES, THE SALE IS MADE IN
ACCORDANCE WITH RULE 144 UNDER THE ACT, OR THE COMPANY RECEIVES AN OPINION OF
COUNSEL FOR THE HOLDER OF THESE SECURITIES REASONABLY SATISFACTORY TO THE
COMPANY, STATING THAT SUCH SALE, TRANSFER, ASSIGNMENT OR HYPOTHECATION IS
EXEMPT FROM THE REGISTRATION AND PROSPECTUS DELIVERY REQUIREMENTS OF SUCH ACT."

          (c)  Any legend required to be placed thereon by the federal or state
securities authorities.

     8.   Warranties and Representations. In connection with the proposed
purchase of the Stock, the Founder hereby agrees, represents and warrants as
follows:

          (a)  The Founder is purchasing the Stock solely for his own account
for investment and not with a view to, or for resale in connection with, any
distribution thereof within the meaning of the Securities Act of 1933 as
amended (the "Act"). The Founder further represents that he or she does not
have any present intention of selling, offering to sell or otherwise disposing
of or distributing the Stock or any portion thereof; and that the entire legal
and beneficial interest of the Stock he or she is purchasing is being purchased
for, and will be held for the account of, the Founder only and neither in whole
nor in part for any other person.

          (b)  The Founder is aware of the Company's business affairs and
financial condition and has acquired sufficient information about the Company
to reach an informed and knowledgeable decision to acquire the Stock. The
Founder further represents and warrants that he or she has discussed the
Company and its plans, operations and financial condition with its officers,
has received all such information as he or she deems necessary and appropriate
to enable him or her to evaluate the financial risk inherent in making an
investment in the Stock and has received satisfactory and complete information
concerning the business and financial condition of the Company in response to
all inquiries in respect thereof.

          (c)  The Founder realizes that his or her purchase of the Stock will
be a highly speculative investment, and he is able, without impairing his
financial condition, to hold the Stock for an indefinite period of time and to
suffer a complete loss on his investment.

          (d)  The Company has disclosed to the Founder that:

               (i)  The sale of the Stock has not been registered under the Act,
and the Stock must be held indefinitely unless a transfer of it is
subsequently registered under the Act or an examination from such registration
is available, and that the Company is under no obligation to register the Stock;

               (ii) The Company will make a notation in its records of the
aforementioned restrictions on transfer and legends.

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<PAGE>   7
     9.   Escrow. As security for his faithful performance of the terms of this
Agreement and to ensure the availability for delivery of the Stock upon
exercise of the Unvested Share Repurchase Option and the Right of First Refusal
herein provided for, the Founder agrees to deliver to and deposit with Gray Cary
Ware & Freidenrich, a Professional Corporation (the "Escrow Agent"), as Escrow
Agent in this transaction, two Stock Assignments duly endorsed (with date and
number of shares blank) in the form attached hereto as Exhibit B, together with
the certificate or certificates evidencing the Stock. Such documents shall be
held by the Escrow Agent pursuant to the Joint Escrow Instructions of the
Company and the Founder set forth in Exhibit C attached hereto and incorporated
by this reference, which instructions shall also be delivered to the Escrow
Agent at the closing hereunder.

     10.  Transfers in Violation of Agreement. The Company shall not be
required (i) to transfer on its books any shares of Stock of the Company which
shall have been sold or transferred in violation of any of the provisions set
forth in this Agreement or (ii) to treat as owner of such shares or to accord
the right to vote as such owner or to pay dividends to any transferee to whom
such shares shall have been so transferred.

     11.  Rights as Shareholder. Subject to the provisions of this Agreement,
the Founder shall exercise all rights and privileges of a shareholder of the
Company with respect to the Stock deposited in escrow.

     12.  Further Instruments. The parties agree to execute such further
instruments and to take such further action as may reasonably be necessary to
carry out the intent of this Agreement.

     13.  "Market Stand-Off" Agreement. Founder hereby agrees that in
connection with the IPO, during the period of duration (not to exceed 180 days)
specified by the Company and an underwriter of common stock of the Company
following the effective date of the registration statement of the Company filed
under the Securities Act with respect to the IPO, he shall not, to the extent
requested by the Company and such underwriter, directly or indirectly sell,
offer to sell, contract to sell (including, without limitation, any short
sale), grant any option to purchase, pledge or otherwise transfer or dispose of
(other than to donees who agree to be similarly bound) any securities of the
Company held by him at any time during such period except common stock included
in such registration. Founder agrees to the terms of any form of such a
stand-off agreement as approved by the company or the underwriter of the IPO.

     14.  Notice. Any notice required or permitted hereunder shall be given in
writing and shall be deemed effectively given upon personal delivery, upon
deposit in the United States Post Office, by registered or certified mail with
postage and fees prepaid, or upon delivery to an overnight courier service
addressed to the other party at the address hereinafter shown below his
signature or at such other address as such party may designate by ten (10)
days' advance written notice to the other party.

     15.  Successors and Assigns. This Agreement shall inure to the benefit of,
and be binding upon, the successors and assigns of each party, including,
without limitation, in the case of the Founder, Founder's heirs, executors,
administrators, successors and assigns.

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<PAGE>   8
     16.  Entire Agreement; Amendments. This Agreement, together with the
Exhibits hereto, shall be construed under the laws of the State of California
(as it applies to agreements between California residents, entered into and to
be performed entirely within California), and constitutes the entire agreement
of the parties with respect to the subject matter hereof superseding all prior
written or oral agreements, and no amendment or addition hereto shall be deemed
effective unless agreed to in writing by the parties.

     17.  Right to Specific Performance. The Founder agrees that the Company
shall be entitled to a decree of specific performance of the terms hereof or an
injunction restraining violation of this Agreement, said right to be in addition
to any other remedies available to the Company.

     18.  Separability. If any provision of this Agreement is held by a court
of competent jurisdiction to be invalid, void or unenforceable, the remaining
provisions shall nevertheless continue in full force and effect without being
impaired or invalidated in any way and shall be construed in accordance with
the purposes and tenor and effect of this Agreement.

     19.  Tax Consequences and Tax Election Notification.

          (a)  The Founder understands that Section 83 of the Internal Revenue
Code of 1986, as amended (the "Code") taxes as ordinary income the difference
between the amount paid for the Stock and the fair market value of the Stock as
of the date any restrictions on the Stock lapse. In this context, "restriction"
means the right of the Company to buy back the stock pursuant to the Unvested
Share Repurchase Option. The Founder understands that he or she may elect to be
taxed at the time the Stock is purchased rather than when and as the Unvested
Share Repurchase Option expires by filing an election under Section 83(b) of
the Code with the Internal Revenue Service (the "IRS") within 30 days from the
date of purchase. Even if the fair market value of the stock equals the amount
paid for the Stock, the election must be made to avoid adverse tax consequences
in the future. The Founder understands that failure to make this filing timely
will result in the recognition of ordinary income by the Founder, as the
Unvested Share Repurchase Option lapses, on the difference between the purchase
price and the fair market value of the Stock at the time such restriction
lapses.

          (b)  The Founder understands that the purchase price of the Stock has
been set by the Board of Directors and that the Company believes this valuation
is a fair attempt to appraise it. The Founder understands, however, that if the
Founder files a Section 83(b) election, the Company can give no assurances that
the purchase price will be accepted as the fair market value of the Stock by
the IRS, and that the IRS could assert that the value of the Stock on the date
of purchase was substantially greater than the purchase price.

          If the IRS were to successfully argue in a tax determination that the
Stock had a value greater than the price paid by the Founder, and the Founder
has filed a Section 83(b) election, the additional value would constitute
ordinary income as of the date of its receipt. The additional taxes (and
interest) due would be payable by the Founder. There is no provision for the
Company to reimburse the Founder for any potential tax liability, and the
Founder assumes all responsibility for any such liability. If the additional
value attributed to the Stock was more than 25 percent of the Founder's gross
income for the year in which that value was taxable, the

                                       8

<PAGE>   9
IRS would have six years from the due date for filing of the Founder's the
return (or the actual filing date of the return if filed thereafter) within
which to assess the additional tax and interest.

     THE FOUNDER ACKNOWLEDGES THAT IT IS THE FOUNDER'S SOLE RESPONSIBILITY AND
NOT THE COMPANY'S RESPONSIBILITY TO FILE TIMELY THE ELECTION UNDER SECTION
83(B), EVEN IF THE FOUNDER REQUESTS THE COMPANY OR ITS REPRESENTATIVES TO MAKE
THIS FILING ON THE FOUNDER'S BEHALF. THE FOUNDER FURTHER UNDERSTANDS THAT ANY
PURPORTED ELECTION PURSUANT TO SECTION 83(B) MUST COMPLY WITH THE PROVISIONS OF
TREASURY REGULATION SECTION 1.83-2. FOUNDER ACKNOWLEDGES THAT HE HAS BEEN
ADVISED BY THE COMPANY TO SEEK THE ASSISTANCE OF A TAX ADVISOR IN THIS MATTER.

          (c) The Founder shall notify the Company in writing if Founder files
an election pursuant to Section 83(b) of the Code. The Company intends, in the
event it does not receive from Founder evidence of such filing, to claim a tax
deduction for any amount which would be taxable to Founder in the absence of
such an election.

     IN WITNESS WHEREOF, the parties hereto have executed this Agreement as of
the day and year first above written.

"FOUNDER"                               "COMPANY"

/s/ KEVIN GRUNDY                        MachOne Communications, Inc.

KEVIN GRUNDY                            By: /s/ MICHAEL SOLOMON
-------------------------------------       ---------------------------------

Address: 43525 VISTA DEL MAR            Title: CEO
        -----------------------------          ------------------------------
  FREMONT, CA 94539
-------------------------------------

                                       9
<PAGE>   10

                                   EXHIBIT A

                               CONSENT OF SPOUSE

     I, ____________, spouse of ________________, acknowledge that I have read
the Founder Stock Purchase Agreement dated as of ____________, 1998, to which
this Consent is attached as Exhibit A (the "Agreement") and that I know its
contents. I am aware that by its provisions the Company has the option to
purchase certain shares of Stock of the Company which my spouse owns pursuant to
the Agreement including any interest I might have therein, upon termination of
his employment under circumstances set forth in the Agreement, and that certain
other restrictions are imposed upon the sale or other disposition of the Stock
during my spouse's lifetime and in the event of his death.

     I agree that my interest, if any, in the Stock subject to the Agreement
shall be bound by the Agreement and further understand and agree that any
community property interest I may have in the Stock shall be similarly bound by
the Agreement.

     Signed and Dated:
                       -------------------------

                                       10

<PAGE>   11

                                    EXHIBIT B

                      ASSIGNMENT SEPARATE FROM CERTIFICATE

     FOR VALUE RECEIVED, KEVIN GRUNDY hereby sells, assigns and transfers unto
_______________ _____________ (________) shares of the Common Stock of MachOne
Communications, Inc., a California corporation, standing in the undersigned's
name on the books of said corporation represented by Certificate No. ____
herewith, and do hereby irrevocably constitute and appoint _________________
attorney to transfer the said stock on the books of the said corporation with
full power of substitution in the premises.

     Date: _________, 1998              By: /s/  KEVIN GRUNDY
                                            ---------------------------------<PAGE>   1
                                                                   EXHIBIT 10.38

                        FOUNDER STOCK PURCHASE AGREEMENT

     This Founder Stock Purchase Agreement is dated as of the tenth day of June
1998 (the "Effective Date") by and between MachOne Communications, Inc., a
California corporation (the "Company"), and Thomas Obenhuber ("Founder").

                                   WITNESSETH:

     WHEREAS, Founder is a founder and a key employee of the Company.

     WHEREAS, Founder has purchased from the Company 240,000 shares of the
Company's Common Stock (the "Original Shares") pursuant to that certain Founder
Stock Purchase Agreement, by and between Company and Founder, dated as of
December 23, 1997 (the "Initial Purchase Agreement").

     WHEREAS, the Company desires to issue and the Founder desires to acquire
stock of the Company as herein described, on the terms and conditions
hereinafter set forth.

     NOW, THEREFORE, IT IS AGREED between the parties as follows:

     1. Number of Shares and Price Per Share. The Founder hereby agrees to
purchase from the Company and the Company agrees to sell to the Founder five
hundred sixty thousand (560,000) shares of the Company's Common Stock (the
"Stock") with a fair market value of $5,600 (or $0.01 per share). The
consideration for the Stock (the "Purchase Price") will be paid by Founder in
cash, by check, or promissory note concurrent with the execution of this
Agreement against the Company's delivery of a stock certificate evidencing the
Stock.

     2. Unvested Share Repurchase Option. The Company shall have the option (the
"Unvested Share Repurchase Option") to reacquire any shares purchased pursuant
to this Agreement which have not vested in the Founder pursuant to subsection
2(a) (the "Unvested Shares") under the terms set forth in this Section 2.

          (a) Vesting of Shares. Founder shall purchase the Stock effective upon
the date first written above, but the "Initial Vesting Date" for determination
of vesting of the Stock shall be December 3, 1997. The shares of Stock purchased
by the Founder will vest (the "Vested Shares") on and after the Initial Vesting
Date in accordance with the following formula:

                                       1
<PAGE>   2

<TABLE>
<CAPTION>
Date                                    Number of Shares Vested
----                                    -----------------------
<S>                                     <C>
On the Initial Vesting Date             81,666 shares of Stock will
                                        vest (14.5837%)

For each full month of the Company's    An additional 2.0833% of the
continuous employment of Founder        Stock will vest (11,667 shares)
following the Initial Vesting Date      for each full month of service.
</TABLE>

     Provided that the aggregate number of shares of Stock constituting Vested
Shares may not exceed 560,000 shares (as adjusted for stock splits and the
like). In the event a fraction of a share is vested, the number of vested shares
shall be rounded to the nearest whole number. The parties acknowledge that
nothing in this Agreement shall revise or alter the vesting provisions for the
Original shares as set forth in the Initial Purchase Agreement.

          (b) Exercise of Unvested Share Repurchase Option. If the Founder's
employment with the Company is terminated for any reason, with or without cause,
voluntarily or involuntarily, including termination due to death or disability
(as defined below), or if the Founder or the Founder's legal representative
attempts to dispose of any Unvested Shares other than as allowed in this
Agreement, the Company may exercise the Unvested Share Repurchase Option by
written notice to the Escrow Agent (as defined in Section 8) and to the Founder
or the Founder's legal representative within 60 days after such termination or
after the Company has received notice of the attempted disposition.

          (c) Payment for Shares and Return of Shares. Payment by the Company to
the Escrow Agent on behalf of the Founder or the Founder's legal representative
shall be made in cash within 60 days after the date of the mailing of the
written notice of exercise of the Unvested Share Repurchase Option. For purposes
of the foregoing, cancellation of any promissory note of the Founder to the
Company shall be treated as payment to the Founder in cash to the extent of the
unpaid principal and any accrued interest canceled. The purchase price per share
being purchased by the Company pursuant to the Unvested Share Repurchase Option
shall be $0.001 per share, adjusted appropriately to reflect any stock split,
stock dividend, recapitalization, etc. Within 30 days after payment by the
Company, the Escrow Agent shall give the shares which the Company has purchased
to the Company and shall give the payment received from the Company to the
Founder.

          (d) Early Termination of Unvested Share Repurchase Option. The other
provisions of Section 2 notwithstanding, upon any Transfer of Control (as
defined below), the Unvested Share Repurchase Option shall terminate as of a
date prior to the Transfer of Control, as the Board so determines pursuant to
the definition below, or if no such determination is made, two days prior to the
closing of the transaction involving the Transfer of Control. Any such
termination that was permissible solely by reason of this subsection 2(d) shall
be conditioned upon the consummation of the Transfer of Control. For purposes of
this subsection 2(d), a Transfer of Control shall be deemed to have occurred
upon any of the following events: (i) the direct or indirect sale or exchange by
the shareholders of the Company of all or substantially all of the stock of the
Company where the shareholders of the Company before such sale or

                                       2
<PAGE>   3

exchange do not retain, directly or indirectly, at least a majority of the
beneficial interest in the voting stock of the Company; (ii) a merger in which
the shareholders of the Company before the merger do not retain, directly or
indirectly, at least a majority of the beneficial interest in the voting stock
of the Company; or (iii) the sale, exchange, or transfer of all or substantially
all of the Company's assets (other than a sale, exchange, or transfer to one or
more corporations where the shareholders of the Company before such sale,
exchange, or transfer retain, directly or indirectly, at least a majority of the
beneficial interest in the voting stock of the corporation(s) to which the
assets were transferred).

     For the purposes of early termination of the unvested share repurchase
option, a Transfer of Control shall be deemed to have occurred only if one of
the events described in the paragraph above has occurred and, within one year of
such event: (i) there is a decrease in Founder's base salary and/or bonus
compensation; (ii); (iii) there is a material breach by Company (or its
successor or assign) of this Agreement or of Founder's Employment Agreement with
the Company; (iv) the Company fails to obtain the assumption of this Agreement
and the Employment Agreement by MachOne's successor or assign; or (v) MachOne
(or its successor or assign) fails to continue Founder's opportunity to
participate, on the same or more favorable terms, in benefit or compensation
programs in which Founder was participating prior to the transfer of control.

          (e) Transfers Not Subject to the Unvested Share Repurchase Option.
The Unvested Share Repurchase Option shall not apply to a transfer of shares of
the Stock to the Founder's ancestors, descendants or spouse or to a trustee for
their benefit or the benefit of the Founder, provided that such transferee shall
agree in writing (in a form satisfactory to the Company) to take the shares of
the Stock subject to all the terms and conditions of this Section 2.

          (f) Assignment of Unvested Share Repurchase Option. The Company may
assign the Unvested Share Repurchase Option to one or more persons, who shall
have the right to exercise the Unvested Share Repurchase Option in his or her
own name for his or her own account.

     3. Right of First Refusal. Before any shares of the Stock registered in
the name of Founder may be sold or transferred (including transfer by operation
of law), such shares shall first be offered to the Company, which will have the
right to purchase all or any part of such shares proposed to be transferred
("Right of First Refusal"), in the following manner:

          (a) Transfer Notice. The Founder or his or her legal representative
shall first give written notice (the "Transfer Notice") of any proposed transfer
to the Company. The Transfer Notice shall name the proposed transferee, state
the number of shares of Stock to be transferred, the price per share and all
other terms of the offer. The Transfer Notice shall be signed by the Founder or
his or her representative and the prospective transferee and must constitute a
binding agreement for the transfer of the Stock subject only to the Right of
First Refusal.

                                       3
<PAGE>   4

          (b) Bona Fide Determination. Within 30 days of delivery of the
Transfer Notice, the Company's Board of Directors shall determine the bona fide
nature of the proposed transfer and give the Founder written notice of its
determination. If the proposed transfer is deemed to be bona fide, the remaining
subsections of this section shall apply to the sale. If the proposed transfer is
deemed not to be bona fide, the Founder will be responsible for providing
additional information to the Board to show the bona fide nature of the proposed
transfer and no Stock will be transferred on the books of the Company until the
Board has approved the proposed transfer as bona fide.

          (c) Failure to Exercise; Exercise. If the Company elects not to or
fails to exercise in full the Right of First Refusal within 30 days from the
later of the date the Transfer Notice is delivered to the Company or 30 days
after the date the transfer is determined to be bona fide (if the Founder is
required to provide additional information as provided in Section 3(b)), the
Founder may, by the later of 60 days after the delivery of the Transfer Notice
to the Company or 30 days after the date the transfer is determined to be bona
fide (if the Founder is required to provide additional information as provided
in Section 3(b)), conclude a transfer of the shares of Stock subject to the
Transfer Notice which have not been purchased by the Company pursuant to
exercise of the Right of First Refusal on the terms and conditions described in
the Transfer Notice. Any proposed transfer on terms and conditions different
from those described in the Transfer Notice, as well as any subsequent proposed
transfer by the Founder, shall again be subject to the Fight of First Refusal
and shall require compliance by the Founder with the procedure described in this
Section 3. If the Company exercises the Right of First Refusal, the parties
shall consummate the sale of shares of Stock on the terms set forth in the
Transfer Notice by the later of 60 days after the delivery of the Transfer
Notice to the Company or 30 days after the date the transfer is determined to be
bona fide (if the Purchaser is required to provide additional information as
provided in Section 3(b)); provided, however, in the event the Transfer Notice
provides for the payment for the shares of Stock other than in cash, the Company
shall have the option of paying for the shares of Stock by the discounted cash
equivalent of the consideration described in the Transfer Notice as reasonably
determined by the Company.

          (d) Condition to Transfer. All transferees of shares of Stock or any
interest therein other than the Company shall be required as a condition of such
transfer to agree in writing (in a form satisfactory to the Company) that they
will receive and hold such shares of Stock or interests subject to the
provisions of this Agreement, including the Right of First Refusal.

          (e) Assignment of Right of First Refusal. The Company may assign the
Right of First Refusal to one or more persons, who shall have the right to
exercise the Right of First Refusal in his or her own name for his or her own
account.

          (f) Termination. The Right of First Refusal will terminate upon the
closing of a firm commitment underwritten public offering to the public of the
Company's Common Stock pursuant to a registration statement under the Securities
Act of 1933, as amended (the "IPO").

          (g) Transfer Not Subject to Right of First Refusal. The Right of First
Refusal shall not apply to a transfer of shares of the Stock to the Founder's
ancestors, descendants or

                                       4
<PAGE>   5

spouse or to a trustee for their benefit or the benefit of the Founder, provided
that such transferee shall agree in writing (in a form satisfactory to the
Company) to take the shares of Stock subject to all the terms and conditions of
this Section 3.

     4.   Piggyback Registration Rights.

          (a) If the Company shall determine to register any of its securities
either for its own account or the account of a shareholder(s) exercising demand
registration rights, other than a registration relating solely to employee
benefit plans, or a registration relating solely to a transaction pursuant to
Rule 145 promulgated under the Securities Act of 1933, or a registration on any
registration form which does not permit secondary sales or does not include
substantially the same information as would be required to be included in a
registration statement covering the sale of the Stock, the Company will promptly
give to the Founder written notice thereof and include in such registration (and
any related qualification under blue sky laws), and in any underwriting involved
therein, the number of Vested Shares specified in a written request made by the
Founder within fifteen (15) days after receipt of such written notice from the
Company, except as set forth in Section 4(b) below.

          (b) If the registration of which the Company gives notice is for a
registered public offering involving an underwriting, the right of any Founder
to registration shall be conditioned upon the Founder's participation in such
underwriting and the inclusion of such Founder's Stock in the underwriting
pursuant to an underwriting agreement in customary form with the underwriter or
underwriters selected by the Company. Notwithstanding any other provision of
this Section, if the underwriter reasonably determines that marketing factors
require a limitation on the number of shares to be underwritten the underwriter
may exclude some or all of the Stock with the number of shares that may be
included in the registration and underwriting being allocated among the Founder
and all other shareholders entitled to have securities included in such
registration in proportion, as nearly as practicable, to the respective amounts
of securities which they had requested to be included in such registration
(provided, however, that if the registration is for the account of shareholders
exercising demand registration rights, the number of shares that may be included
by the Founder shall be cut back entirely before any limitation on the number of
shares that may be included by such shareholders).

          (c) All expenses of the registration shall be borne by the Company,
except underwriting discounts and selling commissions applicable to the sale of
any of Founder's Stock and any other securities of the Company being sold in the
same registration by other shareholders, which shall be borne by the Founder and
such other shareholders pro rata on the basis of the number of their shares
registered.

     5. Stock Dividends, etc. If, from time to time, there is any stock
dividend, stock split or other change in the character or amount of any of the
outstanding stock of the Company, then in such event any and all new substituted
or additional securities to which Founder is entitled by reason of Founder's
ownership of Unvested Shares or Stock shall be immediately subject to the
Unvested Share Repurchase Option or the Right of First Refusal, respectively,
with the same force and effect as the Unvested Shares or Stock.

                                       5
<PAGE>   6

     6. Consent of Spouse. If the Founder is married on the date of this
Agreement, the Founder's spouse shall execute a Consent of Spouse in the form of
Exhibit A hereto, effective on the date hereof Such consent shall not be deemed
to confer or convey to the spouse any rights in the Stock that do not otherwise
exist by operation of law or the agreement of the parties. If the Founder should
marry or remarry subsequent to the date of this Agreement, the Founder shall
within thirty (30) days thereafter obtain his or her new spouse's acknowledgment
of and consent to the existence and binding effect of all restrictions contained
in this Agreement by signing an additional Consent of Spouse in the form of
Exhibit A.

     7. Legends. All certificates representing any shares of Stock subject to
the provisions of this Agreement shall have endorsed thereon the following
legends:

          (a) "THE SHARES REPRESENTED BY THIS CERTIFICATE ARE SUBJECT TO A
REPURCHASE OPTION AND RIGHT OF FIRST REFUSAL IN FAVOR OF THE COMPANY OR ITS
ASSIGNEE SET FORTH IN AN AGREEMENT BETWEEN THE COMPANY AND THE REGISTERED
HOLDER, OR HIS OR HER PREDECESSOR IN INTEREST, A COPY OF WHICH IS ON FILE AT THE
PRINCIPAL OFFICE OF THIS COMPANY.

          (b) "THE SECURITIES EVIDENCED BY THIS CERTIFICATE HAVE NOT BEEN
REGISTERED UNDER THE SECURITIES ACT OF 1933, AS AMENDED, AND MAY NOT BE SOLD,
TRANSFERRED, ASSIGNED OR HYPOTHECATED UNLESS THERE IS AN EFFECTIVE REGISTRATION
STATEMENT UNDER SUCH ACT COVERING SUCH SECURITIES, THE SALE IS MADE IN
ACCORDANCE WITH RULE 144 UNDER THE ACT, OR THE COMPANY RECEIVES AN OPINION OF
COUNSEL FOR THE HOLDER OF THESE SECURITIES REASONABLY SATISFACTORY TO THE
COMPANY, STATING THAT SUCH SALE, TRANSFER, ASSIGNMENT OR HYPOTHECATION IS EXEMPT
FROM THE REGISTRATION AND PROSPECTUS DELIVERY REQUIREMENTS OF SUCH ACT."

          (c) Any legend required to be placed thereon by the federal or state
securities authorities.

     8. Warranties and Representations. In connection with
the proposed purchase of the Stock, the Founder hereby agrees, represents and
warrants as follows:

          (a) The Founder is purchasing the Stock solely for his own account for
investment and not with a view to, or for resale in connection with, any
distribution thereof within the meaning of the Securities Act of 1933 as amended
(the "Act"). The Founder further represents that he or she does not have any
present intention of selling, offering to sell or otherwise disposing of or
distributing the Stock or any portion thereof; and that the entire legal and
beneficial interest of the Stock he or she is purchasing is being purchased for,
and will be held for the account of, the Founder only and neither in whole nor
in part for any other person.

          (b) The Founder is aware of the Company's business affairs and
financial condition and has acquired sufficient information about the Company to
reach an informed and knowledgeable decision to acquire the Stock. The Founder
further represents and warrants that

                                       6
<PAGE>   7

he or she has discussed the Company and its plans, operations and financial
condition with its officers, has received all such information as he or she
deems necessary and appropriate to enable him or her to evaluate the financial
risk inherent in making an investment in the Stock and has received satisfactory
and complete information concerning the business and financial condition of the
Company in response to all inquiries in respect thereof.

          (c) The Founder realizes that his or her purchase of the Stock will be
a highly speculative investment, and he is able, without impairing his financial
condition, to hold the Stock for an indefinite period of time and to suffer a
complete loss on his investment.

          (d) The Company has disclosed to the Founder that:

               (i) The sale of the Stock has not been registered under the Act,
and the Stock must be held indefinitely unless a transfer of it is subsequently
registered under the Act or an exemption from such registration is available,
and that the Company is under no obligation to register the Stock;

               (ii) The Company will make a notation in its records of the
aforementioned restrictions on transfer and legends.

     9. Escrow. As security for his faithful performance of the terms of this
Agreement and to ensure the availability for delivery of the Stock upon exercise
of the Unvested Share Repurchase Option and the Right of First Refusal herein
provided for, the Founder agrees to deliver to and deposit with Gray Cary Ware &
Freidenrich, a Professional Corporation (the "Escrow Agent"), as Escrow Agent in
this transaction, two Stock Assignments duly endorsed (with date and number of
shares blank) in the form attached hereto as Exhibit B. together with the
certificate or certificates evidencing the Stock. Such documents shall be held
by the Escrow Agent pursuant to the Joint Escrow Instructions of the Company and
the Founder set forth in Exhibit C attached hereto and incorporated by this
reference, which instructions shall also be delivered to the Escrow Agent at the
closing hereunder.

     10. Transfers in Violation of Agreement. The Company shall not be required
(i) to transfer on its books any shares of Stock of the Company which shall have
been sold or transferred in violation of any of the provisions set forth in this
Agreement or (ii) to treat as owner of such shares or to accord the right to
vote as such owner or to pay dividends to any transferee to whom such shares
shall have been so transferred.

     11. Rights as Shareholder. Subject to the provisions of this Agreement, the
Founder shall exercise all rights and privileges of a shareholder of the Company
with respect to the Stock deposited in escrow.

     12. Further Instruments. The parties agree to execute such further
instruments and to take such further action as may reasonably be necessary to
carry out the intent of this Agreement.

     13. "Market Stand-Off" Agreement. Founder hereby agrees that in connection
with the IPO, during the period of duration (not to exceed 180 days) specified
by the Company and an underwriter of common stock of the Company following the
effective date of the registration

                                       7
<PAGE>   8

statement of the Company filed under the Securities Act with respect to the IPO,
he shall not, to the extent requested by the Company and such underwriter,
directly or indirectly sell, offer to sell, contract to sell (including, without
limitation, any short sale), grant any option to purchase, pledge or otherwise
transfer or dispose of (other than to donees who agree to be similarly bound)
any securities of the Company held by him at any time during such period except
common stock included in such registration. Founder agrees to the terms of any
form of such a stand-off agreement as approved by the company or the underwriter
of the IPO.

     14. Notice. Any notice required or permitted hereunder shall be given in
writing and shall be deemed effectively given upon personal delivery, upon
deposit in the United States Post Office, by registered or certified mail with
postage and fees prepaid, or upon delivery to an overnight courier service
addressed to the other party at the address hereinafter shown below his
signature or at such other address as such party may designate by ten (10) days'
advance written notice to the other party.

     15. Successors and Assigns. This Agreement shall inure to the benefit of,
and be binding upon, the successors and assigns of each party, including,
without limitation, in the case of the Founder, Founder's heirs, executors,
administrators, successors and assigns.

     16. Entire Agreement: Amendments. This Agreement together with the Exhibits
hereto, shall be construed under the laws of the State of California (as it
applies to agreements between California residents, entered into and to be
performed entirely within California), and constitutes the entire agreement of
the parties with respect to the subject matter hereof superseding all prior
written or oral agreements, and no amendment or addition hereto shall be deemed
effective unless agreed to in writing by the parties.

     17. Right to Specific Performance. The Founder agrees that the Company
shall be entitled to a decree of specific performance of the terms hereof or an
injunction restraining violation of this Agreement, said right to be in addition
to any other remedies available to the Company.

     18. Separability. If any provision of this Agreement is held by a court of
competent jurisdiction to be invalid, void or unenforceable, the remaining
provisions shall nevertheless continue in full force and effect without being
impaired or invalidated in any way and shall be construed in accordance with the
purposes and tenor and effect of this Agreement.

     19. Tax Consequences and Tax Election Notification.

        (a) The Founder understands that Section 83 of the Internal Revenue Code
of 1986, as amended (the "Code") taxes as ordinary income the difference between
the amount paid for the Stock and the fair market value of the Stock as of the
date any restrictions on the Stock lapse. In this context, "restriction" means
the right of the Company to buy back the stock pursuant to the Unvested Share
Repurchase Option. The Founder understands that he or she may elect to be taxed
at the time the Stock is purchased rather than when and as the Unvested Share
Repurchase Option expires by filing an election under Section 83(b) of the Code
with the Internal Revenue Service (the "IRS") within 30 days from the date of
purchase. Even if the fair market value of the Stock equals the amount paid for
the Stock, the election must be made to

                                       8
<PAGE>   9

avoid adverse tax consequences in the future. The Founder understands that
failure to make this filing timely will result in the recognition of ordinary
income by the Founder, as the Unvested Share Repurchase Option lapses, on the
difference between the purchase price and the fair market value of the Stock at
the time such restriction lapses.

          (b) The Founder understands that the purchase price of the Stock has
been set by the Board of Directors and that the Company believes this valuation
is a fair attempt to appraise it. The Founder understands, however, that if the
Founder files a Section 83(b) election, the Company can give no assurances that
the purchase price will be accepted as the fair market value of the Stock by the
IRS, and that the IRS could assert that the value of the Stock on the date of
purchase was substantially greater than the purchase price.

          If the IRS were to successfully argue in a tax determination that the
Stock had a value greater than the price paid by the Founder, and the Founder
has filed a Section 83(b) election, the additional value would constitute
ordinary income as of the date of its receipt. The additional taxes (and
interest) due would be payable by the Founder. There is no provision for the
Company to reimburse the Founder for any potential tax liability, and the
Founder assumes all responsibility for any such liability. If the additional
value attributed to the Stock was more than 25 percent of the Founder's gross
income for the year in which that value was taxable, the IRS would have six
years from the due date for filing of the Founder's the return (or the actual
filing date of the return if filed thereafter) within which to assess the
additional tax and interest.

     THE FOUNDER ACKNOWLEDGES THAT IT IS THE FOUNDER'S SOLE RESPONSIBILITY AND
NOT THE COMPANY'S RESPONSIBILITY TO FILE TIMELY THE ELECTION UNDER SECTION
83(B), EVEN IF THE FOUNDER REQUESTS THE COMPANY OR ITS REPRESENTATIVES TO MAKE
THIS FILING ON THE FOUNDER'S BEHALF. THE FOUNDER FURTHER UNDERSTANDS THAT ANY
PURPORTED ELECTION PURSUANT TO SECTION 83(B) MUST COMPLY WITH THE PROVISIONS OF
TREASURY REGULATION SECTION 1.83-2. FOUNDER ACKNOWLEDGES THAT HE HAS BEEN
ADVISED BY THE COMPANY TO SEEK THE ASSISTANCE OF A TAX ADVISOR TN THIS MATTER.

          (c) The Founder shall notify the Company in writing if Founder files
an election pursuant to Section 83(b) of the Code. The Company intends, in the
event it does not receive from Founder evidence of such filing, to claim a tax
deduction for any amount which would be taxable to Founder in the absence of
such an election.

                                       9
<PAGE>   10

     IN WITNESS WHEREOF, the parties hereto have executed this Agreement as of
the day and year first above written.

"FOUNDER"                               "COMPANY"

                                        MachOne Communications, Inc.

/s/ THOMAS OBENHUBER                    By: [SIGNATURE ILLEGIBLE]
-------------------------------------       ---------------------------------

Address: 712 Wisconsin St.              Title: CEO
         ----------------------------          ------------------------------

         San Francisco, CA 94107
         ----------------------------

                                       10
<PAGE>   11

                                    EXHIBIT A

                                CONSENT OF SPOUSE

     I, ____________________, spouse of _____________________ acknowledge that I
have read the Founder Stock Purchase Agreement dated as of ______________ 1998,
to which this Consent is attached as Exhibit A (the "Agreement") and that I know
its contents. I am aware that by its provisions the Company has the option to
purchase certain shares of Stock of the Company which my spouse owns pursuant to
the Agreement including any interest I might have therein, upon termination of
his employment under circumstances set forth in the Agreement, and that certain
other restrictions are imposed upon the sale or other disposition of the Stock
during my spouse's lifetime and in the event of his death.

     I agree that my interest, if any, in the Stock subject to the Agreement
shall be bound by the Agreement and further understand and agree that any
community property interest I may have in the Stock shall be similarly bound by
the Agreement.

     Signed and Dated: ______________________.

                                       11
<PAGE>   12

                                    EXHIBIT B

                      ASSIGNMENT SEPARATE FROM CERTIFICATE

     FOR VALUE RECEIVED, ____________________ hereby sells, assigns and
transfers unto ___________________ _________________ (___) shares of the Common
Stock of MachOne Communications, Inc., a California corporation, standing in the
undersigned's name on the books of said corporation represented by Certificate
No. ___ herewith, and do hereby irrevocably constitute and appoint _____
attorney to transfer the said stock on the books of the said corporation with
full power of substitution in the premises.

     Date: June __, 1998                By:
                                            ------------------------------------

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