<PAGE>   1
                                                                   EXHIBIT 10.15


                       RESTRICTED STOCK PURCHASE AGREEMENT


      This Restricted Stock Purchase Agreement (this "AGREEMENT") is made and
entered into as of September 10, 1996 (the "EFFECTIVE DATE") by and between
Aptex Software Inc., a California corporation (the "COMPANY"), and Michael A.
Thiemann ("PURCHASER").

                                 R E C I T A L S

      A. Purchaser is an employee of the Company and this Agreement is being
entered into pursuant to the Company's 1996 Equity Incentive Plan, as such may
hereafter be amended in accordance with its terms (the "PLAN"). The Plan is a
written compensatory benefit plan within the meaning of Rule 701 under the
Securities Act of 1933, as amended (the "1933 ACT").

      B. The Plan and the issuance of shares of the Company's Common Stock under
this Agreement are intended to qualify for the exemption afforded by Section
25102(o) of the California Corporate Securities Law of 1968, as amended.

      NOW THEREFORE, in consideration of the facts stated in the foregoing
recitals, the Company and Purchaser hereby agree as follows:

      1.    PURCHASE OF SHARES.

            (a) AGREEMENT; SHARES. On the Effective Date and subject to the
terms and conditions of this Agreement and the Plan, Purchaser hereby purchases
from the Company, and Company hereby sells to Purchaser, an aggregate of
1,000,000 Shares of the Company's Common Stock (the "SHARES") at an aggregate
purchase price of $30,000 (the "PURCHASE PRICE") or $0.03 per Share (the
"PURCHASE PRICE PER SHARE"), which the Company's Board of Directors has
determined to be the fair market value of the Shares. As used in this Agreement,
the term "SHARES" refers to the Shares purchased under this Agreement and
includes all securities received (a) in replacement of the Shares, (b) as a
result of stock dividends or stock splits in respect of the Shares, and (c) in
replacement of the Shares in a recapitalization, merger, reorganization or the
like.

            (b) PLAN TERMS INCORPORATED BY REFERENCE. A copy of the Plan is
attached hereto as Exhibit 1 and the terms and conditions of the Plan are hereby
incorporated into this Agreement by reference. Any capitalized terms not defined
in this Agreement shall have the meanings given to such terms in the Plan. This
Agreement is a Restricted Stock Award within the meaning of the Plan.

      2.    PAYMENT OF PURCHASE PRICE; CLOSING.

            (a) DELIVERIES BY PURCHASER. Purchaser hereby delivers to the
Company the full Purchase Price in cash in the amount of $30,000. Purchaser also
hereby delivers to the Company: (i) two (2) copies of a blank Stock Power and
Assignment Separate from Stock Certificate in the form of Exhibit 2 attached
hereto (the "STOCK POWERS"), both executed by Purchaser (and Purchaser's spouse,
if any), and (ii) if Purchaser is married, a Consent of Spouse in the form of
Exhibit 3 attached hereto (the "SPOUSE CONSENT") duly executed by Purchaser's
spouse.




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            (b) DELIVERIES BY THE COMPANY. Upon its receipt of the entire
Purchase Price from Purchaser and all the documents to be executed and delivered
by Purchaser to the Company under Section 2(a), the Company will issue a duly
executed stock certificate evidencing the Shares in the name of Purchaser
registered in Purchaser's name, with such certificate to be placed in escrow as
provided in Section 9 until expiration or termination of each of: (i) the
Company's Vesting Repurchase Option set forth in Section 5; (ii) the General
Repurchase Option granted to HNC Software Inc., a Delaware corporation ("HNC")
pursuant to the Plan and Section 6 of this Agreement; and (iii) the Company's
Right of First Refusal set forth in Section 7.

            (c) INVESTORS' RIGHTS AGREEMENT. Concurrently herewith, the Company,
Purchaser and HNC shall enter into, execute and deliver to each other an
Investors' Rights Agreement in substantially the form of Exhibit 4 hereto.

      3.    REPRESENTATIONS AND WARRANTIES OF PURCHASER.  Purchaser hereby
represents and warrants to the Company that:

            (a) PURCHASE FOR OWN ACCOUNT FOR INVESTMENT. Purchaser is purchasing
the Shares for Purchaser's own account for investment purposes only and not with
a view to, or for sale in connection with, a distribution of the Shares within
the meaning of the 1933 Act. Purchaser has no present intention of selling or
otherwise disposing of all or any portion of the Shares and no one other than
Purchaser has any beneficial ownership of any of the Shares.

            (b) ACCESS TO INFORMATION AND PLAN. Purchaser has had access to all
information regarding the Company and its present and prospective business,
assets, liabilities and financial condition that Purchaser reasonably considers
important in making the decision to purchase the Shares, and Purchaser has had
ample opportunity to ask questions of the Company's representatives concerning
such matters and this investment. Purchaser acknowledges that Purchaser has
received and reviewed a copy of the Plan.

            (c) UNDERSTANDING OF RISKS. Purchaser is a founder of the Company
and is fully aware of: (i) the highly speculative nature of the investment in
the Shares; (ii) the financial hazards involved; (iii) the lack of liquidity of
the Shares and the restrictions on transferability of the Shares (e.g., that
Purchaser may not be able to sell or dispose of the Shares or use them as
collateral for loans); (iv) the qualifications and backgrounds of the management
of the Company; and (v) the tax consequences of Purchaser's investment in the
Shares.

            (d) PURCHASER'S QUALIFICATIONS. Purchaser has a preexisting personal
or business relationship with the Company and/or certain of its officers and
directors of a nature and duration sufficient to make Purchaser aware of the
character, business acumen and general business and financial circumstances of
the Company and/or such officers and directors. By reason of Purchaser's
business or financial experience, Purchaser is capable of evaluating the merits
and risks of this investment, has the ability to protect Purchaser's own
interests in this transaction and is financially capable of bearing a total loss
of this investment. Purchaser is an "accredited investor" within the meaning of
Regulation D promulgated under the 1933 Act.

            (e) NO GENERAL SOLICITATION. At no time was Purchaser presented with
or solicited by any publicly issued or circulated newspaper, mail, radio,
television or other form of general advertising or solicitation in connection
with the offer, sale and purchase of the Shares.




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            (f) COMPLIANCE WITH SECURITIES LAWS. Purchaser understands and
acknowledges that, in reliance upon the representations and warranties made by
Purchaser herein, the Shares are not being registered with the Securities and
Exchange Commission ("SEC") under the 1933 Act or being qualified under the
California Corporate Securities Law of 1968, as amended (the "LAW"), but instead
are being issued under exemptions from the registration and qualification
requirements of the 1933 Act and the Law which impose certain restrictions on
Purchaser's ability to transfer the Shares.

            (g) RESTRICTIONS ON TRANSFER; REPURCHASE RIGHTS. Purchaser
understands that Purchaser may not transfer any Shares unless such Shares are
registered under the 1933 Act or qualified under the Law or unless, in the
opinion of counsel to the Company, exemptions from such registration and
qualification requirements are available. Purchaser understands that only the
Company may file a registration statement with the SEC or the California
Commissioner of Corporations and that the Company is under no obligation to do
so with respect to the Shares. Purchaser has also been advised that exemptions
from registration and qualification may not be available or may not permit
Purchaser to transfer all or any of the Shares in the amounts or at the times
proposed by Purchaser. Purchaser also understands that, in addition to the above
securities law restrictions, this Agreement imposes: (i) contractual
restrictions on Purchaser's ability to transfer, pledge or encumber the Shares,
and (ii) contractual options that may require Purchaser to sell the Shares back
to the Company, HNC or others on the terms and conditions set forth in this
Agreement and in the Plan.

            (h) RULE 144. In addition, Purchaser has been advised that SEC Rule
144 promulgated under the 1933 Act, which permits certain limited sales of
unregistered securities, is not presently available with respect to the Shares
and, in any event, requires that the Shares be held for a minimum of two years,
and in certain cases three years, after they have been purchased and paid for
(within the meaning of Rule 144), before they may be resold under Rule 144.

            (i) RULE 701. Under the currently effective provisions of Rule 701
promulgated by the SEC under the 1933 Act, the Shares will become freely
tradeable by Purchaser (if Purchase not then an affiliate of the Company),
subject to limited conditions regarding the method of sale, ninety (90) days
after the first sale of Common Stock of the Company to the general public
pursuant to a registration statement filed with and declared effective by the
SEC, subject to the lengthier market standoff agreement contained in this
Agreement or in any other agreement entered into by Purchaser. Under such Rule
701, if Purchaser is an affiliate of the Company then Purchaser must comply with
the provisions (other than the holding period requirements) of Rule 144 in
reselling Shares.


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      4. COMPLIANCE WITH CALIFORNIA SECURITIES LAWS. THE SALE OF THE SECURITIES
THAT ARE THE SUBJECT OF THIS AGREEMENT, IF NOT YET QUALIFIED WITH THE CALIFORNIA
COMMISSIONER OF CORPORATIONS AND NOT EXEMPT FROM SUCH QUALIFICATION, IS SUBJECT
TO SUCH QUALIFICATION, AND THE ISSUANCE OF SUCH SECURITIES, AND THE RECEIPT OF
ANY PART OF THE CONSIDERATION THEREFOR PRIOR TO SUCH QUALIFICATION IS UNLAWFUL
UNLESS THE SALE IS EXEMPT. THE RIGHTS OF THE PARTIES TO THIS AGREEMENT ARE
EXPRESSLY CONDITIONED UPON SUCH QUALIFICATION BEING OBTAINED OR AN EXEMPTION
BEING AVAILABLE.

      5. COMPANY'S VESTING REPURCHASE OPTION. Purchaser agrees that the Company
(and/or its assignee(s)) shall have the right, at its sole option, to repurchase
all or a portion of the Unvested Shares (as defined below) from Purchaser on the
terms set forth in this Section if Purchaser ceases to be employed by the
Company (as defined herein) for any reason, or no reason, including without
limitation Purchaser's death, disability, voluntary resignation or termination
by the Company with or without cause (the "VESTING REPURCHASE OPTION").

            (a) "EMPLOYED BY THE COMPANY" AND "TERMINATION DATE." For purposes
of this Agreement, Purchaser will be considered to be "EMPLOYED BY THE COMPANY"
if the Board of Directors of the Company determines that Purchaser is rendering
substantial services as an officer, employee, consultant or independent
contractor to the Company or to any subsidiary of the Company. In case of any
dispute as to whether Purchaser is employed by the Company, the Board of
Directors of the Company will have discretion to determine whether Purchaser has
ceased to be employed by the Company or any subsidiary of the Company and the
effective date on which Purchaser's employment terminated (the "TERMINATION
DATE").

            (b) UNVESTED AND VESTED SHARES. Shares that are not Vested Shares
(as defined in this Section) are "UNVESTED SHARES." On the Effective Date all of
the Shares will be Unvested Shares. If Purchaser has been continuously employed
by the Company at all times from the Effective Date until January 1, 1997 (the
"FIRST VESTING DATE"), then on the First Vesting Date twenty-five percent (25%)
of the Shares will become Vested Shares; and thereafter, for so long (and only
for so long) as Purchaser remains continuously employed by the Company: (i) on
February 1, 1997, and on the first day of each successive calendar month
thereafter, an additional one forty-eighth (1/48) of the Shares will become
Vested Shares; and (ii) on January 1, 2000 all of the Shares will be Vested
Shares. Subject to Sections 5(c) and (d) below, no Shares will become Vested
Shares after the Termination Date.

            (c) VESTING OF SHARES UPON TERMINATION "WITHOUT CAUSE."
Notwithstanding anything to the contrary herein, in the event that, on or before
January 1, 2000, Purchaser's employment with the Company is terminated by the
Company "without Cause" (as such term is defined in that certain Employment
Agreement dated of even date herewith by and between the Company and Purchaser
(the "EMPLOYMENT AGREEMENT")), then, effective upon such termination without
Cause, a number of Unvested Shares equal to the lesser of (i) twelve and
one-half percent (12.5%) of the Shares, or (ii) all then remaining Unvested
Shares, will become Vested Shares.

            (d) VESTING OF SHARES UPON CERTAIN BUSINESS COMBINATIONS. In the
event that (i) a Business Combination (as defined below) occurs on or before
January 1, 2000; and (ii) Purchaser's employment with the Company is terminated
"without Cause" (as such term is defined in the Employment Agreement) after the
consummation of such Business Combination and on or




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<PAGE>   5

before January 1, 2000, then, effective upon such termination of Purchaser's
employment with the Company without Cause, all of the Shares that are then
Unvested Shares shall become Vested Shares. As used in this subsection 5(d) the
term "BUSINESS COMBINATION" shall mean: (i) a consolidation or merger of the
Company with or into any other corporation or corporations that results in the
holders of the Company's outstanding capital stock immediately prior to such
consolidation or merger owning, immediately after such consolidation or merger,
Stock (as defined below) representing less than fifty percent (50%) of the
voting power of all of the then outstanding capital stock of the surviving
corporation of such consolidation or merger or of the parent (or ultimate
parent) corporation of such surviving corporation; (ii) a sale of all or
substantially all the assets of the Company; or (iii) any transaction or series
of related transactions in which shareholders of the Company sell or otherwise
transfer to a single party (or group of related parties) (other than to HNC or
the Company) outstanding capital stock of the Company that represents more than
fifty percent (50%) of the voting power of all of the Company's then outstanding
capital stock. As used in this subsection 5(d), the term "STOCK" means either
capital stock of the Company that was outstanding immediately prior to a
consolidation or merger referred to in clause (i) of the preceding sentence, or
stock of another corporation that is issued to the shareholders of the Company
in such consolidation or merger in respect of their ownership of capital stock
of the Company.



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            (e) ADJUSTMENTS. The number of Shares that are Vested Shares or
Unvested Shares, as determined by the provisions of this Agreement, will be
proportionally adjusted to reflect any stock dividend, stock split, reverse
stock split or similar recapitalization of the Common Stock of the Company
occurring after the Effective Date.

            (f) EXERCISE OF VESTING REPURCHASE OPTION. At any time within thirty
(30) days after the Termination Date, the Company may elect to repurchase any or
all of the Unvested Shares by giving Purchaser written notice of exercise of the
Vesting Repurchase Option. The Company will then have the option to repurchase
from Purchaser (or from Purchaser's personal representative, as the case may be)
any or all of the Unvested Shares at the Purchaser's original Purchase Price Per
Share (as adjusted to reflect any stock dividend, stock split, reverse stock
split or similar recapitalization of the Common Stock of the Company occurring
after the Effective Date). The parties acknowledge that the Company's Repurchase
Option may be assigned in whole or in part to HNC; provided, however, that if
the Company assigns the Repurchase Option, then the assignee of the Repurchase
Option must pay the Company upon assignment of the Repurchase Option cash in an
amount equal to (i) the fair market value of the Unvested Shares minus (ii) the
product obtained by multiplying the original Purchase Price Per Share (as
adjusted as provided above) by the number of shares that are Unvested Shares.

            (g) PAYMENT OF REPURCHASE PRICE. The repurchase price payable to
purchase Unvested Shares upon exercise of the Vesting Repurchase Option will be
payable, at the option of the Company or its assignee(s), by check. The
repurchase price will be paid without interest within sixty (60) days after the
Termination Date.

            (h) RIGHT OF TERMINATION UNAFFECTED. Nothing in this Agreement will
be construed to limit or otherwise affect in any manner whatsoever the right or
power of the Company (or any parent, subsidiary or affiliate of the Company) to
terminate Purchaser's employment at any time for any reason or no reason, with
or without cause.

      6. GENERAL REPURCHASE OPTION. As a material inducement and consideration
to HNC to enter into that certain Series A Preferred Stock Purchase Agreement
dated of even date herewith (the "HNC PURCHASE AGREEMENT"), and as a material
inducement and consideration to the Company to sell the Shares to Purchaser
pursuant to this Agreement for the Purchase Price, Purchaser agrees with the
Company and with HNC that, as provided in the Plan and pursuant to the HNC
Purchase Agreement (and in addition to the Vesting Repurchase Option), at any
time during the Repurchase Period (as that term is defined in the Plan) HNC
shall have the right, at its sole option, to repurchase all (but not less than
all) of the Shares (whether they are Vested Shares or Unvested Shares) at the
Share Repurchase Price (as that term is defined in the Plan) in accordance with
the provisions of this Section 6 and the provisions of the Plan, specifically
including the provisions of Section 22 of the Plan entitled "General Repurchase
Option" (the "GENERAL REPURCHASE OPTION").

            (a)   ACKNOWLEDGEMENT AND AGREEMENT.  PURCHASER HEREBY FURTHER
ACKNOWLEDGES AND AGREES THAT:

                  (i) PURCHASER HAS READ AND UNDERSTANDS THE PLAN (INCLUDING
WITHOUT LIMITATION THE PROVISIONS OF SECTION 22 OF THE PLAN REGARDING THE
GENERAL REPURCHASE OPTION, THE DEFINITION OF THE "REPURCHASE PERIOD" AND THE
PROVISIONS OF THE PLAN REGARDING THE DETERMINATION OF THE "SHARE REPURCHASE
PRICE" AT WHICH THE SHARES MAY BE PURCHASED PURSUANT TO THE GENERAL REPURCHASE
OPTION);


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                  (ii) A COPY OF THE PLAN IS ATTACHED AS EXHIBIT 1 TO THIS
AGREEMENT AND THE PROVISIONS OF THE PLAN (INCLUDING WITHOUT LIMITATION THE
PROVISIONS OF SECTION 22 OF THE PLAN REGARDING THE GENERAL REPURCHASE OPTION)
ARE INCORPORATED BY REFERENCE IN THIS AGREEMENT AND FORM PART OF THE PROVISIONS
OF THIS AGREEMENT; AND

                  (iii) PURCHASER AND THE SHARES ARE BOUND BY THE GENERAL
REPURCHASE OPTION AND THE PROVISIONS OF THE PLAN (INCLUDING WITHOUT LIMITATION
THE PROVISIONS OF SECTION 22 OF THE PLAN REGARDING THE GENERAL REPURCHASE
OPTION).

            (b) GENERAL REPURCHASE OPTION PREVAILS. In case of any inconsistency
or conflict between the Company's attempted exercise of the Vesting Repurchase
Option and/or the Right of First Refusal under Sections 5 and/or 7 hereof, and
HNC's attempted exercise of the General Repurchase Option granted under this
Section 6 and under Section 22 of the Plan, the General Repurchase Option shall
supersede, govern and prevail and the Vesting Repurchase Option and the Right of
First Refusal may not be exercised to the extent they are inconsistent or in
conflict with HNC's rights or ability to exercise the General Repurchase Option.
The exercise by the Company (but not its assignees) of a repurchase option or
right of first refusal that results in the Company's repurchase and
reacquisition of Shares at a time when the General Repurchase Option is not
being exercised will not be deemed inconsistent or in conflict with the General
Repurchase Option.

            (c) TERM. The termination of Purchaser's employment with the Company
for any reason shall not terminate the General Repurchase Option and shall have
no effect whatsoever on the General Repurchase Option, which shall remain in
full force and effect in accordance with its terms with respect to any of the
Shares.

            (d) CONSTRUCTION. The parties acknowledge and agree that the
provisions of this Section 6 have been included in this Agreement in order to
carry out the provisions of Section 22 of the Plan regarding HNC's General
Repurchase Option (the "PLAN REPURCHASE OPTION PROVISIONS"). Accordingly, in
case of any conflict or inconsistency between the provisions of this Section 6
and the Plan Repurchase Option Provisions, the provisions of this Section 6
shall be construed and interpreted in a manner consistent with the terms,
conditions, construction and interpretation of the Plan Repurchase Option
Provisions.

      7. RIGHT OF FIRST REFUSAL. Unvested Shares may not be sold or otherwise
transferred by Purchaser without the Company's prior written consent. In
addition, Shares that are subject to the General Repurchase Option ("OPTION
SHARES") may not be transferred by Purchaser without HNC's prior written consent
unless the transferee who acquires such Option Shares first agrees, in a writing
that is reasonably satisfactory to HNC and that is signed by HNC and such
transferee, that the General Repurchase Option and the restrictions and
provisions of this sentence shall continue to apply to and bind all such Option
Shares in the hands of such transferee and its transferees, successors and
assigns. As used herein, the term "TRANSFERABLE SHARES" means Vested Shares that
either (i) are not Option Shares, or (ii) are Option Shares as to which HNC has
given Purchaser HNC's prior written consent to transfer in accordance with the
foregoing provisions of this Section. Subject to the foregoing provisions of
this Section and the terms and conditions of this Agreement and the Plan, before
any Transferable Shares held by Purchaser or any transferee of such Shares
(either being sometimes referred to herein as the "HOLDER") may be sold or
otherwise transferred (including without limitation a transfer by gift or
operation of law), the Company and/or its assignee(s) shall have a right of
first refusal to purchase the Transferable Shares to be sold or




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<PAGE>   8

transferred (the "OFFERED SHARES") on the terms and conditions set forth in this
Section (the "RIGHT OF FIRST REFUSAL").

            (a) NOTICE OF PROPOSED TRANSFER. The Holder of the Offered Shares
will deliver to the Company a written notice (the "NOTICE") stating: (i) the
Holder's bona fide intention to sell or otherwise transfer the Offered Shares;
(ii) the name of each proposed purchaser or other transferee of any Offered
Shares ("PROPOSED TRANSFEREE"); (iii) the number of Offered Shares to be
transferred to each Proposed Transferee; (iv) the bona fide cash price or other
consideration for which the Holder proposes to transfer the Offered Shares (the
"OFFERED PRICE"); and (v) that the Holder will offer to sell the Offered Shares
to the Company and/or its assignee(s) at the Offered Price as provided in this
Section.

            (b) EXERCISE OF RIGHT OF FIRST REFUSAL. At any time within thirty
(30) days after the date of the Notice, the Company and/or its assignee(s) may,
by giving written notice to the Holder, elect to purchase all (but not less than
all) of the Offered Shares proposed to be transferred to any one or more of the
Proposed Transferees named in the Notice, at the purchase price determined in
accordance with subsection (c) below.

            (c) PURCHASE PRICE. The purchase price for the Offered Shares
purchased under this Section will be the Offered Price. If the Offered Price
includes consideration other than cash, then the value of the non-cash
consideration as determined in good faith by the Company's Board of Directors
will conclusively be deemed to be the cash equivalent value of such non-cash
consideration.

            (d) PAYMENT. Payment of the purchase price for Offered Shares will
be payable, at the option of the Company and/or its assignee(s) (as applicable),
by check or by cancellation of all or a portion of any outstanding indebtedness
of the Holder to the Company (or to such assignee, in the case of a purchase of
Offered Shares by such assignee) or by any combination thereof. The purchase
price will be paid without interest within sixty (60) days after the Company's
receipt of the Notice, or, at the option of the Company and/or its assignee(s),
in the manner and at the time(s) set forth in the Notice.

            (e) HOLDER'S RIGHT TO TRANSFER. If all of the Offered Shares
proposed in the Notice to be transferred to a given Proposed Transferee are not
purchased by the Company and/or its assignee(s) as provided in this Section,
then the Holder may sell or otherwise transfer such Offered Shares to that
Proposed Transferee at the Offered Price or at a higher price, provided that
such sale or other transfer is consummated within 120 days after the date of the
Notice, and provided further, that: (i) any such sale or other transfer is
effected in compliance with all applicable securities laws; and (ii) the
Proposed Transferee agrees in writing that the provisions of this Section will
continue to apply to the Offered Shares in the hands of such Proposed
Transferee. If the Offered Shares described in the Notice are not transferred to
the Proposed Transferee within such 120 day period, then a new Notice must be
given to the Company, and the Company will again be offered the Right of First
Refusal before any Shares held by the Holder may be sold or otherwise
transferred.

            (f) EXEMPT TRANSFERS. Notwithstanding anything to the contrary in
this Section, the following transfers of Shares will be exempt from the Right of
First Refusal: (i) the transfer of any or all of the Shares during Purchaser's
lifetime by gift or on Purchaser's death by will or intestacy to Purchaser's
"immediate family" (as defined below) or to a trust for the benefit of Purchaser
or Purchaser's immediate family, provided that each transferee or other
recipient agrees in a writing satisfactory to the Company and HNC that the
General Repurchase Option set forth in



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<PAGE>   9

Section 6 (if such General Repurchase Option has not expired by its terms) and
the provisions of this Section will continue to apply to the transferred Shares
in the hands of such transferee or other recipient; (ii) any transfer of Shares
made pursuant to a statutory merger or statutory consolidation of the Company
with or into another corporation or corporations (except that the Right of First
Refusal will continue to apply thereafter to such Shares, in which case the
surviving corporation of such merger or consolidation shall succeed to the
rights or the Company under this Section unless the agreement of merger or
consolidation expressly otherwise provides); or (iii) any transfer of Shares
pursuant to the winding up and dissolution of the Company. As used herein, the
term "IMMEDIATE FAMILY" will mean Purchaser's spouse, lineal descendant or
antecedent, father, mother, brother or sister, adopted child or grandchild, or
the spouse of any child, adopted child, grandchild or adopted grandchild of
Purchaser.

            (g) TERMINATION OF RIGHT OF FIRST REFUSAL. The Right of First
Refusal will terminate as to all Shares on the effective date of the first sale
of Common Stock of the Company to the general public pursuant to a registration
statement filed with and declared effective by the SEC under the 1933 Act (other
than a registration statement relating solely to the issuance of Common Stock
pursuant to a business combination or an employee incentive or benefit plan).

            (h) ENCUMBRANCES ON TRANSFERABLE SHARES. Purchaser may grant a lien
or security interest in, or pledge, hypothecate or encumber Transferable Shares
only with the prior written consent of the Company and (if the General
Repurchase Option has not terminated) HNC, and only if each party to whom such
lien or security interest is granted, or to whom such pledge, hypothecation or
other encumbrance is made, agrees in a writing satisfactory to the Company and
(so long as the General Repurchase Option has not terminated) HNC that (i) such
lien, security interest, pledge, hypothecation or encumbrance will not apply to
such Transferable Shares after they are acquired by the Company and/or its
assignees pursuant to the Right of First Refusal set forth in this Section or by
HNC pursuant to the General Repurchase Option set forth in Section 6; and (ii)
the provisions of this Section and Section 6 will continue to apply to such
Transferable Shares in the hands of such party and any transferee of such party.
Purchaser may not grant a lien or security interest in, or pledge, hypothecate
or encumber, any Unvested Shares or any other Shares that are not Transferable
Shares.

      8. RIGHTS AS SHAREHOLDER. Subject to the terms and conditions of this
Agreement and the Plan, Purchaser will have all of the rights of a shareholder
of the Company with respect to the Shares from and after the date that Purchaser
delivers payment of the Purchase Price to the Company until such time as
Purchaser disposes of the Shares or the Company and/or its assignee(s) or HNC
exercise(s) the Vesting Repurchase Option, the General Repurchase Option or the
Right of First Refusal with respect to such Shares. Upon an exercise of the
Vesting Repurchase Option, the General Repurchase Option or the Right of First
Refusal, Purchaser will have no further rights as a holder of the Shares so
purchased upon such exercise, except the right to receive payment for the Shares
so purchased in accordance with the provisions of this Agreement and the Plan,
and Purchaser will promptly surrender the stock certificate(s) evidencing the
Shares so purchased to the Company or HNC, as applicable, for transfer or
cancellation.

      9. ESCROW. As security for Purchaser's faithful performance of this
Agreement, Purchaser agrees, immediately upon receipt of the stock
certificate(s) evidencing the Shares, to deliver such certificate(s), together
with the Stock Powers executed by Purchaser and by Purchaser's spouse, if any
(with the date and number of Shares left blank), to the Secretary of the Company
or other designee of the Company ("ESCROW HOLDER"), who is hereby appointed to
hold such



                                      -9-
<PAGE>   10


certificate(s) and Stock Powers in escrow and to take all such actions
and to effectuate all such transfers and/or releases of such Shares as are in
accordance with the terms of this Agreement and the Plan. Purchaser and the
Company agree that Escrow Holder will not be liable to any party to this
Agreement (or to any other party) for any actions or omissions unless Escrow
Holder is grossly negligent or intentionally fraudulent in carrying out the
duties of Escrow Holder under this Section. Escrow Holder may rely upon any
letter, notice or other document executed by any signature purported to be
genuine and may rely on the advice of counsel and obey any order of any court
with respect to the transactions contemplated by this Agreement. The Shares will
be released from escrow only upon the termination of each of the Vesting
Repurchase Option, the General Repurchase Option and the Right of First Refusal;
provided that the certificates representing the Shares shall be released from
escrow to HNC (or its successors or assigns) upon exercise of the General
Repurchase Option.

      10. TAX CONSEQUENCES. Purchaser hereby acknowledges that Purchaser has
been informed that, unless an election if filed by the Purchaser with the
Internal Revenue Service (and, if necessary, the proper state taxing
authorities), within 30 days of the purchase of the Shares, electing pursuant to
Section 83(b) of the Internal Revenue Code (and similar state tax provisions, if
applicable) to be taxed currently on any difference between the Purchase Price
of the Shares and their fair market value on the date of purchase, there will be
a recognition of the taxable income to the Purchaser, measured by the excess, if
any, of the fair market value of the Vested Shares, at the time they cease to be
Unvested Shares, over the purchase price for such Shares. Purchaser represents
that Purchaser has consulted any tax consultant(s) that Purchaser deems
advisable in connection with Purchaser's purchase of the Shares and the filing
of the election under Section 83(b) and similar tax provisions. A form for
Election under Section 83(b) is attached hereto as Exhibit 5 for reference.
PURCHASER HEREBY ASSUMES ALL RESPONSIBILITY FOR FILING SUCH ELECTION AND PAYING
ANY TAXES RESULTING FROM SUCH ELECTION OR FOR FAILING TO FILE THE ELECTION AND
PAYING TAXES RESULTING FROM THE LAPSE OF THE REPURCHASE RESTRICTIONS ON THE
UNVESTED SHARES.

      11.   RESTRICTIVE LEGENDS AND STOP-TRANSFER ORDERS.

            (A) LEGENDS. Purchaser understands and agrees that the Company will
place the legends set forth below or similar legends on any stock certificate(s)
evidencing the Shares, together with any other legends that may be required by
state or federal securities laws, the Company's Articles of Incorporation or
Bylaws, any other agreement between Purchaser and the Company or any agreement
between Purchaser and any third party (including without limitation HNC):

            THE SECURITIES REPRESENTED HEREBY HAVE NOT BEEN REGISTERED UNDER THE
            SECURITIES ACT OF 1933, AS AMENDED (THE "ACT"), OR UNDER THE
            SECURITIES LAWS OF CERTAIN STATES. THESE SECURITIES ARE SUBJECT TO
            RESTRICTIONS ON TRANSFERABILITY AND RESALE AND MAY NOT BE
            TRANSFERRED OR RESOLD EXCEPT AS PERMITTED UNDER THE ACT AND
            APPLICABLE STATE SECURITIES LAWS, PURSUANT TO REGISTRATION OR
            EXEMPTION THEREFROM. INVESTORS SHOULD BE AWARE THAT THEY MAY BE
            REQUIRED TO BEAR THE FINANCIAL RISKS OF THIS INVESTMENT FOR AN
            INDEFINITE PERIOD OF TIME. THE ISSUER OF THESE SECURITIES MAY
            REQUIRE AN OPINION OF COUNSEL IN FORM AND SUBSTANCE



                                      -10-
<PAGE>   11

            SATISFACTORY TO THE ISSUER TO THE EFFECT THAT ANY PROPOSED TRANSFER
            OR RESALE IS IN COMPLIANCE WITH THE ACT AND ANY APPLICABLE STATE
            SECURITIES LAWS.

            THE SHARES REPRESENTED BY THIS CERTIFICATE ARE SUBJECT TO CERTAIN
            RESTRICTIONS ON PUBLIC RESALE AND TRANSFER, A REPURCHASE OPTION HELD
            BY THE ISSUER OF THESE SHARES AND/OR ITS ASSIGNEE(S), A REPURCHASE
            OPTION HELD BY HNC SOFTWARE INC. ("HNC") AND A RIGHT OF FIRST
            REFUSAL OPTION HELD BY THE ISSUER AND/OR ITS ASSIGNEE(S) AS SET
            FORTH IN A RESTRICTED STOCK PURCHASE AGREEMENT BETWEEN THE ISSUER
            AND THE ORIGINAL HOLDER OF THESE SHARES, A COPY OF WHICH MAY BE
            OBTAINED AT THE PRINCIPAL OFFICE OF THE ISSUER. SUCH PUBLIC SALE AND
            TRANSFER RESTRICTIONS, REPURCHASE OPTIONS AND RIGHT OF FIRST REFUSAL
            ARE BINDING ON ALL TRANSFEREES OF THESE SHARES.

            (b) STOP-TRANSFER INSTRUCTIONS. Purchaser agrees that, in order to
ensure compliance with the restrictions imposed by this Agreement, the Company
may issue appropriate "stop-transfer" instructions to its transfer agent, if
any, and if the Company transfers its own securities, it may make appropriate
notations to the same effect in its own records.

            (c) REFUSAL TO TRANSFER. The Company will not be required (i) to
transfer on its books any Shares that have been sold or otherwise transferred in
violation of any of the provisions of this Agreement or (ii) to treat as owner
of such Shares, or to accord the right to vote or pay dividends, to any
purchaser or other transferee to whom such Shares have been so transferred.

      12. MARKET STANDOFF AGREEMENT. Purchaser agrees in connection with any
registration of the Company's securities under the 1933 Act that, upon the
request of the Company or the underwriters managing any registered public
offering of the Company's securities, Purchaser will not sell or otherwise
dispose of any Shares without the prior written consent of the Company or such
managing underwriters, as the case may be, for a period of time (not to exceed
180 days) after the effective date of such registration requested by such
managing underwriters and subject to all restrictions as the Company or the
managing underwriters may specify for employee-shareholders generally.

      13. COMPLIANCE WITH LAWS AND REGULATIONS. The issuance and transfer of the
Shares will be subject to and conditioned upon compliance by the Company and
Purchaser with all applicable state and federal laws and regulations and with
all applicable requirements of any stock exchange or automated quotation system
on which the Company's Common Stock may be listed or quoted at the time of such
issuance or transfer.

      14. SUCCESSORS AND ASSIGNS. The Company may assign any of its rights under
this Agreement, including its rights to repurchase Shares under the Vesting
Repurchase Option, and the Right of First Refusal. Such rights may be assigned,
without limitation, to HNC. This Agreement will be binding upon and inure to the
benefit of the successors and assigns of the Company and (to the extent
applicable), HNC. Subject to the restrictions on transfer herein set forth, this
Agreement will be binding upon Purchaser and Purchaser's heirs, executors,
administrators,




                                      -11-
<PAGE>   12

successors and assigns. HNC's rights under the General Repurchase Option may be
assigned to any corporation with whom HNC is merged or consolidated with or into
in any consolidation, merger or similar business combination or to whom HNC
sells or transfers all or substantially all its assets.

      15. GOVERNING LAW; SEVERABILITY. This Agreement will be governed by and
construed in accordance with the internal laws of the State of California,
excluding that body of laws pertaining to conflict of laws. If any provision of
this Agreement is determined by a court of law to be illegal or unenforceable,
then such provision will not be voided but rather will be enforced to the
maximum extent possible and the other provisions will remain fully effective and
enforceable.

      16. NOTICES. Any notice required or permitted hereunder will be given in
writing and will be deemed to have been effectively given (i) upon personal
delivery, (ii) three (3) days after deposit in the United States mail by
certified or registered mail (return receipt requested), (iii) one (1) business
day after its deposit with any return receipt express courier (prepaid), or (iv)
one (1) business day after transmission by telecopier, addressed to the
receiving party at its address (or facsimile number, in the case of transmission
by telecopier) as shown below or to such other address as such party may
designate in writing from time to time to the other party in accordance with
this Section.

            If to the Company:
            ------------------

            Aptex Software Inc.
            9605 Scranton Road, Suite 240
            San Diego, California 92121
            Fax:  (619) 623-0558

            If to Purchaser:
            ----------------

            Michael A. Thiemann
            3516 Crown Point Drive
            San Diego, California 92109
            Fax:  (619) _________

            If to HNC:
            ----------

            HNC Software Inc.
            5930 Cornerstone Court West
            San Diego, California 92121
            Fax:  (619) 452-3220

      17.   FURTHER INSTRUMENTS.  The parties agree to execute such further
instruments and to take such further action as may be reasonably necessary to
carry out the purposes and intent of this Agreement.

      18.   HEADINGS.  The captions and headings of this Agreement are
included for ease of reference only and will be disregarded in interpreting
or construing this Agreement.  All references herein to Sections refer to
Sections of this Agreement.



                                      -12-
<PAGE>   13

      19. AMENDMENT; WAIVER. This Agreement may be amended and modified only by
a writing executed by the Company and Purchaser; provided, however, that no
provision of this Agreement affecting (or potentially affecting) the General
Repurchase Option or any other rights (or potential rights) of HNC hereunder in
any manner may be amended or modified in any respect without the prior written
consent of HNC, which may be withheld in HNC's sole discretion. No rights of the
Company, Purchaser or HNC may be waived except by a writing executed by the
party against whom such waiver is asserted.

      20. HNC THIRD PARTY BENEFICIARY STATUS. The parties acknowledge and agree
that the provisions of this Agreement are being made for the benefit of HNC and
that HNC is an intended third party beneficiary of this Agreement, entitled to
enforce all the terms and conditions of this Agreement (including but not
limited to the provisions of Section 6, Section 7, Section 11, Section 19, this
Section 20 and any other provisions related thereto) against the Company and
Purchaser and their respective successors and assigns, to the same extent that
HNC could if HNC were a party and signatory to this Agreement.

      21. ENTIRE AGREEMENT. This Agreement, together with all its Exhibits, and
the Plan, constitutes the entire agreement and understanding of the parties with
respect to the subject matter of this Agreement, and supersedes all prior
understandings and agreements, whether oral or written, between the parties
hereto with respect to the specific subject matter hereof.

      IN WITNESS WHEREOF, the Company has caused this Agreement to be executed
in duplicate by its duly authorized representative and Purchaser has executed
this Agreement in duplicate, as of the Effective Date.

APTEX SOFTWARE INC.                       PURCHASER

By:
    --------------------------            -------------------------
                                          Michael A. Thiemann
Name:
    --------------------------

Title:
    --------------------------



                                      -13-
<PAGE>   14

                                LIST OF EXHIBITS

Exhibit 1:  Aptex Software Inc. 1996 Equity Incentive Plan (including
            provisions thereof regarding the General Repurchase Option)

Exhibit 2:  Stock Power and Assignment Separate from Stock Certificate

Exhibit 3:  Spousal Consent

Exhibit 4:  Investors' Rights Agreement

Exhibit 5:  Form of Election Under Section 83(b) of the Internal Revenue Code




<PAGE>   15



                                                                       EXHIBIT 1



                APTEX SOFTWARE INC. 1996 EQUITY INCENTIVE PLAN






                                      -2-
<PAGE>   16




                                                                       EXHIBIT 2


                           STOCK POWER AND ASSIGNMENT

                            SEPARATE FROM CERTIFICATE



      FOR VALUE RECEIVED and pursuant to that certain Restricted Stock Purchase
Agreement between MICHAEL A. THIEMANN and APTEX SOFTWARE INC. dated as of
September __, 1996, (the "AGREEMENT"), the undersigned hereby sells, assigns and
transfers unto ______________, __________ shares of the Common Stock of APTEX
SOFTWARE INC., a California corporation (the "COMPANY"), standing in the
undersigned's name on the books of the Company represented by Certificate No(s).
____ delivered herewith, and does hereby irrevocably constitute and appoint the
Secretary of the Company as the undersigned's attorney-in-fact, with full power
of substitution, to transfer said stock on the books of the Company. THIS
ASSIGNMENT MAY ONLY BE USED AS AUTHORIZED BY THE AGREEMENT AND THE EXHIBITS
THERETO AND THE COMPANY'S 1996 EQUITY INCENTIVE PLAN.

Dated:  ______________, 199__


                                      PURCHASER



                                      _____________________________
                                      Michael A. Thiemann


                                      _____________________________
                                      __________________ (Purchaser's Spouse)





INSTRUCTION: Please do not fill in any blanks other than the signature line. The
purpose of this Stock Power and Assignment is to enable the Company and/or its
assignee(s) to acquire the Shares upon exercise of the "Vesting Repurchase
Option" and/or the "Right of First Refusal" set forth in the Agreement or to
enable HNC Software Inc. to acquire the Shares upon exercise of its "General
Repurchase Option" set forth in this Agreement, without requiring additional
signatures on the part of the Purchaser or Purchaser's Spouse.




                                       -3-
<PAGE>   17




                                                                       EXHIBIT 3


                                CONSENT OF SPOUSE



      I, the undersigned, Catherine Thiemann, am the spouse of MICHAEL A.
THIEMANN ("PURCHASER"). I have read and hereby consent to and approve all the
terms and conditions of: (1) the Restricted Stock Purchase Agreement (the
"AGREEMENT") dated September __, 1996 between Purchaser and Aptex Software Inc.,
a California corporation (the "COMPANY"), pursuant to which Purchaser has
purchased 1,000,000 Shares of the Company's Common Stock (the "SHARES") and (2)
an Investors' Rights Agreement dated as of September __, 1996 ("INVESTORS'
AGREEMENT") executed by Purchaser in connection with the Agreement.

      In consideration of the Company granting my spouse, the Purchaser, the
right to purchase the Shares under the Agreement, I hereby agree with the
Company and its successors and assigns, and with HNC Software Inc., and its
successors and assigns, to be irrevocably bound by all the terms and conditions
of the Agreement (including, but not limited to, the Vesting Repurchase Option,
the General Repurchase Option, the Right of First Refusal and the market
standoff agreements contained therein) and further agree that any community
property interest or other interest I may have in or to the Shares will be
irrevocably bound by the Agreement.

      I hereby appoint Purchaser as my attorney-in-fact, to act in my name,
place and stead with respect to any amendment of the Agreement or any actions in
connection therewith.


Dated as of September __, 1996



                                          ___________________________
                                          Catherine Thiemann





                                      -4-
<PAGE>   18





                                                                       EXHIBIT 4





                           INVESTORS' RIGHTS AGREEMENT




                                      -5-
<PAGE>   19



                                                                       EXHIBIT 5

                       ELECTION UNDER SECTION 83(B) OF THE
                              INTERNAL REVENUE CODE



The undersigned Taxpayer hereby elects, pursuant to Section 83(b) of the
Internal Revenue Code, to include in gross income of the Taxpayer's current
taxable year the excess, if any, of the fair market value of the property
described below at the time of transfer over the amount paid for such property,
as compensation for services.

1.    TAXPAYER'S NAME:              Michael A. Thiemann

      TAXPAYER'S ADDRESS:           3516 Crown Point Drive
                                    San Diego, California 92109

      SOCIAL SECURITY NUMBER:       ###-##-####

2.    The property with respect to which the election is made is described as
      follows: 1,000,000 shares of Common Stock of Aptex Software Inc., a
      California corporation (the "COMPANY"), which is Taxpayer's employer for
      the corporation for whom the Taxpayer performs services.

3.    The date on which the Shares were transferred was September __, 1996 and
      this election is made for calendar year 1996.

4.    The Shares are subject to the following restrictions: The Company may
      repurchase all or a portion of the Shares at the Taxpayer's original
      purchase price under certain conditions at the time of Taxpayer's
      termination of employment or services.

5.    The fair market value of the Shares (without regard to restrictions other
      than restrictions which by their terms will never lapse) was $0.03 per
      share at the time of transfer.

6.    The amount paid for such Shares was $ 0.03 per share.

7.    The Taxpayer has submitted a copy of this statement to the Company

      THE ELECTION MUST BE FILED WITH THE INTERNAL REVENUE SERVICE ("IRS"), AT
      THE OFFICE WHERE THE TAXPAYER FILES ANNUAL INCOME TAX RETURNS, WITHIN 30
      DAYS AFTER THE DATE OF TRANSFER OF THE PROPERTY, AND MUST ALSO BE FILED
      WITH THE TAXPAYER'S INCOME TAX RETURNS FOR THE CALENDAR YEAR. THE ELECTION
      CANNOT BE REVOKED WITHOUT THE CONSENT OF THE IRS.



Dated: September __, 1996                 ___________________________
                                          Michael A. Thiemann




                                      -6-