<PAGE>

                                                                   EXHIBIT 10.21

                          BANYAN SYSTEMS INCORPORATED

                  EXECUTIVE OFFICER RESTRICTED STOCK AGREEMENT
                    GRANTED UNDER 1992 STOCK INCENTIVE PLAN


 
     This Restricted Stock Agreement (this "Agreement") is made this 16th day of
October, 1998, between Banyan Systems Incorporated, a Massachusetts corporation
(the "Company"), and Robert D. Burke (the "Participant").

     For valuable consideration, receipt of which is acknowledged, the Company
and the Participant (each, a "Party" and together, the "Parties") each agree as
follows:

     1.   Purchase of Shares.
          ------------------ 

     The Company shall issue and sell to the Participant, and the Participant
shall purchase from the Company, subject to the terms and conditions set forth
in this Agreement and in the Company's 1992 Stock Incentive Plan, as amended
(the "Plan"), 60,000 shares (the "Shares") of common stock, $0.01 par value per
share, of the Company ("Common Stock"), at a purchase price of $0.01 per share.
The aggregate purchase price for the Shares shall be paid by the Participant by
check payable to the order of the Company or such other method as may be
acceptable to the Company. Upon receipt by the Company of payment for the
Shares, the Company shall issue to the Participant one or more certificates in
the name of the Participant for that number of Shares purchased by the
Participant.  The Participant agrees that the Shares shall be subject to the
Purchase Option set forth in Section 2 of this Agreement and the restrictions on
transfer set forth in Section 4 of this Agreement.

     2.   Purchase Option.
          --------------- 

     (a) In the event that the Participant ceases to be employed by the Company
for any reason or no reason, with or without cause, or the Participant announces
his intention to terminate his employment with the Company, prior to October 16,
2001, the Company shall have the right and option (the "Purchase Option") to
purchase from the Participant, for a sum of $0.01 per share (the "Option
Price"), any or all of the Unvested Shares (as defined below).
<PAGE>
 
     "Unvested Shares" means the total number of Shares multiplied by the
Applicable Percentage at the time the Purchase Option becomes exercisable by the
Company.  The "Applicable Percentage" shall be (i) 100% during the 24-month
period ending October 16, 2000, (ii) 60% during the 12-month period ending
October 16, 2001 and (iii) zero on or after October 16, 2001.  Notwithstanding
the foregoing, the Applicable Percentage referred to in clauses (i) and (ii)
above shall each be reduced by one-fifth of 100% and one-third of 60% (e.g.,
from 100% to 80%, from 60% to 40% and from 20% to zero), respectively, in
accordance with each of the following:  (A) on October 16, 1999, if, at any time
after November 30, 1998, the 30 Day Fair Market Value (as defined below) per
share of Common Stock equals or exceeds $6.00, or, on the first such date after
October 16, 1999 when the 30 Day Fair Market Value per share of Common Stock
equals or exceeds $6.00, (B) on April 16, 2000, if, at any time after November
30, 1998, the 30 Day Fair Market Value per share of Common Stock equals or
exceeds $9.00, or, on the first such date after April 16, 2000 when the 30 Day
Fair Market Value per share of Common Stock equals or exceeds $9.00 and (C) on
April 16, 2000, if, any time after November 30, 1998, the 30 Day Fair Market
Value per share of Common Stock equals or exceeds $12.00, or, on the first such
date after April 16, 2000 when the 30 Day Fair Market Value per share of Common
Stock equals or exceeds $12.00.

     The "30 Day Fair Market Value" per share of Common Stock shall be
determined as follows:

          (I)  If the Common Stock is listed on a national securities exchange,
the Nasdaq National Market, the Nasdaq system, or another nationally recognized
exchange or trading system as of the date of calculation, the 30 Day Fair Market
Value per share of Common Stock shall be deemed to be the arithmetic average of
the last reported sale price per share of Common Stock thereon for the 30
trading days ended on the trading day immediately preceding the date of
calculation; or, if no such price is reported for each trading day in such 30-
trading day period, the 30 Day Fair Market Value per share of Common Stock shall
be determined pursuant to the following clause (II).

          (II) If the Common Stock is not listed on a national securities
exchange, the Nasdaq National Market, the Nasdaq system or another nationally
recognized exchange or trading system as of the date of calculation or for each
trading day in such 30-trading day period, the 30 Day Fair Market Value per
share of Common Stock shall be deemed to be the amount most recently determined
by the Board of Directors to represent the fair market value per share of the
Common Stock (including without limitation a determination for purposes of
granting Common Stock options or issuing Common Stock under an employee benefit
plan of the Company); or, if the Board of Directors has not made such a
determination within the two-month period prior to the date of calculation, then
the 30 Day Fair Market Value per share of Common Stock shall be the amount
determined by the Board of Directors in its sole discretion.

                                      -2-
<PAGE>
 
     (b) In the event that the Participant's employment with the Company is
terminated by reason of death or disability, the number of the Shares for which
the Purchase Option becomes exercisable shall be fifty percent (50%) of the
number of Unvested Shares for which the Purchase Option would otherwise become
exercisable. For this purpose, "disability" shall mean the Participant's absence
from the full-time performance of the Participants's duties with the Company for
180 consecutive calendar days as a result of incapacity due to mental or
physical illness which is determined to be total and permanent by a physician
selected by the Company or its insurers and reasonably acceptable to the
Participant or the Participant's legal representative.

     (c) For purposes of this Agreement, employment with the Company shall
include employment with a parent or subsidiary of the Company.

     3.   Exercise of Purchase Option and Closing.
          --------------------------------------- 

     (a) The Company may exercise the Purchase Option by delivering or mailing
to the Participant (or the Participant's estate), within 60 days after the
termination of the employment of the Participant with the Company, a written
notice of exercise of the Purchase Option.  Such notice shall specify the number
of Shares to be purchased.  If and to the extent the Purchase Option is not so
exercised by the giving of such a notice within such 60-day period, the Purchase
Option shall automatically expire and terminate effective upon the expiration of
such 60-day period.

     (b) Within 10 days after delivery to the Participant of the Company's
notice of the exercise of the Purchase Option pursuant to subsection (a) above,
the Participant (or the Participant's estate) shall, pursuant to the provisions
of the Joint Escrow Instructions referred to in Section 8, tender to the Company
at its principal offices the certificate or certificates representing the Shares
which the Company has elected to purchase in accordance with the terms of this
Agreement, duly endorsed in blank or with duly endorsed stock powers attached
thereto, all in form suitable for the transfer of such Shares to the Company.
Promptly following its receipt of such certificate or certificates, the Company
shall pay to the Participant the aggregate Option Price for such Shares
(provided that any delay in making such payment shall not invalidate the
Company's exercise of the Purchase Option with respect to such Shares).

     (c) After the time at which any Shares are required to be delivered to the
Company for transfer to the Company pursuant to subsection (b) above, the
Company shall not pay any dividend to the Participant on account of such Shares
or permit the Participant to exercise any of the privileges or rights of a
stockholder with respect to such Shares, but shall, in so far as permitted by
law, treat the Company as the owner of such Shares.

                                      -3-
<PAGE>
 
     (d) The Option Price may be payable, at the option of the Company, in
cancellation of all or a portion of any outstanding indebtedness of the
Participant to the Company or in cash (by check) or both.

     (e) The Company shall not purchase any fraction of a Share upon exercise of
the Purchase Option, and any fraction of a Share resulting from a computation
made pursuant to Section 2 of this Agreement shall be rounded to the nearest
whole Share (with any one-half Share being rounded upward).

     (f) The Company may assign its Purchase Option to one or more persons or
entities.

     4.   Restrictions on Transfer.
          ------------------------ 

     The Participant shall not sell, assign, transfer, pledge, hypothecate or
otherwise dispose of, by operation of law or otherwise (collectively "transfer")
any Shares, or any interest therein, that are subject to the Purchase Option,
except that the Participant may transfer such Shares to or for the benefit of
any spouse, child or grandchild, or to a trust for their benefit, provided that
                                                                  --------     
such Shares shall remain subject to this Agreement (including without limitation
the restrictions on transfer set forth in this Section 4 and the Purchase
Option), and such permitted transferee shall, as a condition to such transfer,
deliver to the Company a written instrument confirming that such transferee
shall be bound by all of the terms and conditions of this Agreement; or

     5.   Effect of Prohibited Transfer.
          ----------------------------- 

     The Company shall not be required (a) to transfer on its books any of the
Shares which shall have been sold or transferred in violation of any of the
provisions set forth in this Agreement, or (b) to treat as owner of such Shares
or to pay dividends to any transferee to whom any such Shares shall have been so
sold or transferred.

     6.   Escrow.
          ------ 

     The Participant shall, upon the execution of this Agreement, execute Joint
Escrow Instructions in the form attached to this Agreement as Appendix A.  The
                                                              ----------      
Joint Escrow Instructions shall be delivered to the escrow agent thereunder.
The Participant shall deliver to such escrow agent a stock assignment duly
endorsed in blank and hereby instructs the Company to deliver to such escrow
agent, on behalf of the Participant, the certificate(s) evidencing the Shares
issued hereunder.  Such materials shall be held by such escrow agent pursuant to
the terms of such Joint Escrow Instructions.

                                      -4-
<PAGE>
 
     7.   Restrictive Legend.
          ------------------ 

     All certificates representing Shares shall have affixed thereto a legend in
substantially the following form, in addition to any other legends that may be
required under federal or state securities laws:

          "The shares of stock represented by this certificate are subject to
          restrictions on transfer and an option to purchase set forth in a
          certain Restricted Stock Agreement between the corporation and the
          registered owner of these shares (or his predecessor in interest), and
          such Agreement is available for inspection without charge at the
          office of the Secretary of the corporation."

     8.   Provisions of the Plan.
          ---------------------- 

     This Agreement is subject to the provisions of the Plan, a copy of which is
furnished to the Participant with this Agreement.

     9.   Withholding Taxes; Section 83(b) Election.
          ----------------------------------------- 

     (a) The Participant acknowledges and agrees that the Company has the right
to deduct from payments of any kind otherwise due to the Participant any
federal, state or local taxes of any kind required by law to be withheld with
respect to the purchase of the Shares by the Participant or the lapse of the
Purchase Option.

     (b) The Participant acknowledges that he has been informed of the
availability of making an election in accordance with Section 83(b) of the
Internal Revenue Code of 1986, as amended; that such election must be filed with
the Internal Revenue Service within 30 days of the transfer of shares to the
Participant; and that the Participant is solely responsible for making such
election.

     10.  Severability.
          ------------ 

     The invalidity or unenforceability of any provision of this Agreement shall
not affect the validity or enforceability of any other provision of this
Agreement, and each other provision of this Agreement shall be severable and
enforceable to the extent permitted by law.

                                      -5-
<PAGE>
 
     11.  Waiver.
          ------ 
 
     Any provision for the benefit of the Company contained in this Agreement
may be waived, either generally or in any particular instance, by the Board of
Directors of the Company.

     12.  Binding Effect.
          -------------- 

     This Agreement shall be binding upon and inure to the benefit of the
Company and the Participant and their respective heirs, executors,
administrators, legal representatives, successors and assigns, subject to the
restrictions on transfer set forth in Section 4 of this Agreement.

     13.  Notice.
          ------ 

     All notices, instructions and other communications given hereunder or in
connection herewith shall be in writing.  Any such notice, instruction or
communication shall be sent either (i) by registered or certified mail, return
receipt requested, postage prepaid, or (ii) prepaid via a reputable nationwide
overnight courier service, in each case addressed to the Company at Vice
President, Human Resources, Banyan Systems Incorporated, 120 Flanders Road, P.O.
Box 5013, Westboro, Massachusetts 01581-5013, and to the Participant at 30 Allen
Circle, Boxford, Massachusetts  01921 (or to such other address as either the
Company or the Participant may have furnished to the other in writing in
accordance herewith).  Any such notice, instruction or communication shall be
deemed to have been delivered five business days after it is sent by registered
or certified mail, return receipt requested, postage prepaid, or one business
day after it is sent via a reputable nationwide overnight courier service.
Either Party may give any notice, instruction or other communication hereunder
using any other means, but no such notice, instruction or other communication
shall be deemed to have been duly delivered unless and until it actually is
received by the Party for whom it is intended.

     14.  Pronouns.
          -------- 

     Whenever the context may require, any pronouns used in this Agreement shall
include the corresponding masculine, feminine or neuter forms, and the singular
form of nouns and pronouns shall include the plural, and vice versa.

     15.  Entire Agreement.
          ---------------- 

     This Agreement and the Plan constitute the entire agreement between the
Parties, and supersede all prior agreements and understandings, relating to the
subject matter of this Agreement.

                                      -6-
<PAGE>
 
     16.  Amendment.
          --------- 

     This Agreement may be amended or modified only by a written instrument
executed by both the Company and the Participant.

     17.  Governing Law.
          ------------- 

     This Agreement shall be construed, interpreted and enforced in accordance
with the internal laws of the Commonwealth of Massachusetts without regard to
any applicable conflicts of laws.

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


                              BANYAN SYSTEMS INCORPORATED


                              By: /s/ William P. Ferry
                                  --------------------
                                  Name:   William P. Ferry
                                  Title:  Chairman and
                                          Chief Executive Officer


                              PARTICIPANT



                              /s/ Robert D. Burke
                              -------------------
                              Print Name:  Robert D. Burke

                                      -7-
<PAGE>
 
                                                                      Appendix A
                                                                      ----------

                          BANYAN SYSTEMS INCORPORATED

                           JOINT ESCROW INSTRUCTIONS



                                    October 16, 1998

Richard M. Spaulding
Clerk
Banyan Systems Incorporated
120 Flanders Road
P.O. Box 5013
Westboro, Massachusetts 01581-5013


Dear Sir:

     As Escrow Agent for Banyan Systems Incorporated, a Massachusetts
corporation (the "Company"), and the undersigned person ("Holder"), you are
hereby authorized and directed to hold the documents delivered to you pursuant
to the terms of that certain Restricted Stock Agreement (the "Agreement") of
even date herewith, to which a copy of these Joint Escrow Instructions is
attached, in accordance with the following instructions:

     1.   Appointment.  Holder irrevocably authorizes the Company to deposit
          -----------                                                       
with you any certificates evidencing Shares (as defined in the Agreement) to be
held by you hereunder and any additions and substitutions to said Shares.
Holder does hereby irrevocably constitute and appoint you as his attorney-in-
fact and agent for the term of this escrow to execute with respect to such
Shares all documents necessary or appropriate to make such Shares negotiable and
to complete any transaction herein contemplated.  Subject to the provisions of
this paragraph 1 and the terms of the Agreement, Holder shall exercise all
rights and privileges of a stockholder of the Company while the Shares are held
by you.

     2.   Closing of Purchase.
          ------------------- 

     (a)  Upon any purchase by the Company of the Shares pursuant to the
Agreement, the Company shall give to Holder and you a written notice specifying
the 

                                      A-1
<PAGE>
 
purchase price for the Shares, as determined pursuant to the Agreement, and
the time for a closing hereunder (the "Closing") at the principal office of the
Company.  Holder and the Company hereby irrevocably authorize and direct you to
close the transaction contemplated by such notice in accordance with the terms
of said notice.

     (b)  At the Closing, you are directed (a) to date the stock assignment form
or forms necessary for the transfer of the Shares, (b) to fill in on such form
or forms the number of Shares being transferred, and (c) to deliver same,
together with the certificate or certificates evidencing the Shares to be
transferred, to the Company against the simultaneous delivery to you of the
purchase price for the Shares being purchased pursuant to the Agreement.

     3.   Withdrawal.  The Holder shall have the right to withdraw from this
          ----------                                                        
escrow any Shares as to which the Purchase Option (as defined in the Agreement)
has terminated or expired.

     4.   Duties of Escrow Agent.
          ---------------------- 

     (a)  Your duties hereunder may be altered, amended, modified or revoked
only by a writing signed by all of the parties hereto.

     (b)  You shall be obligated only for the performance of such duties as are
specifically set forth herein and may rely and shall be protected in relying or
refraining from acting on any instrument reasonably believed by you to be
genuine and to have been signed or presented by the proper party or parties.
You shall not be personally liable for any act you may do or omit to do
hereunder as Escrow Agent or as attorney-in-fact of Holder while acting in good
faith and in the exercise of your own good judgment, and any act done or omitted
by you pursuant to the advice of your own attorneys shall be conclusive evidence
of such good faith.

     (c)  You are hereby expressly authorized to disregard any and all warnings
given by any of the parties hereto or by any other person or Company, excepting
only orders or process of courts of law, and are hereby expressly authorized to
comply with and obey orders, judgments or decrees of any court.  In case you
obey or comply with any such order, judgment or decree of any court, you shall
not be liable to any of the parties hereto or to any other person, firm or
Company by reason of such compliance, notwithstanding any such order, judgment
or decree being subsequently reversed, modified, annulled, set aside, vacated or
found to have been entered without jurisdiction.

     (d)  You shall not be liable in any respect on account of the identity,
authority or rights of the parties executing or delivering or purporting to
execute or deliver the Agreement or any documents or papers deposited or called
for hereunder.

                                      A-2
<PAGE>
 
     (e)  You shall be entitled to employ such legal counsel and other experts
as you may deem necessary properly to advise you in connection with your
obligations hereunder and may rely upon the advice of such counsel.

     (f)  Your rights and responsibilities as Escrow Agent hereunder shall
terminate if (i) you cease to be Clerk of the Company or (ii) you resign by
written notice to each party.  In the event of a termination under clause (i),
your successor as Clerk shall become Escrow Agent hereunder; in the event of a
termination under clause (ii), the Company shall appoint a successor Escrow
Agent hereunder.

     (g)  If you reasonably require other or further instruments in connection
with these Joint Escrow Instructions or obligations in respect hereto, the
necessary parties hereto shall join in furnishing such instruments.

     (h)  It is understood and agreed that should any dispute arise with respect
to the delivery and/or ownership or right of possession of the securities held
by you hereunder, you are authorized and directed to retain in your possession
without liability to anyone all or any part of said securities until such
dispute shall have been settled either by mutual written agreement of the
parties concerned or by a final order, decree or judgment of a court of
competent jurisdiction after the time for appeal has expired and no appeal has
been perfected, but you shall be under no duty whatsoever to institute or defend
any such proceedings.

     (i)  These Joint Escrow Instructions set forth your sole duties with
respect to any and all matters pertinent hereto and no implied duties or
obligations shall be read into these Joint Escrow Instructions against you.

     (j)  The Company shall indemnify you and hold you harmless against any and
all damages, losses, liabilities, costs, and expenses, including attorneys' fees
and disbursements, for anything done or omitted to be done by you as Escrow
Agent in connection with this Agreement or the performance of your duties
hereunder, except such as shall result from your gross negligence or willful
misconduct.

     5.   Notice.  All notices, instructions and other communications given
          ------                                                           
hereunder or in connection herewith shall be in writing.  Any such notice,
instruction or communication shall be sent to each of the other parties
thereunto entitled either (i) by registered or certified mail, return receipt
requested, postage prepaid, or (ii) prepaid via a reputable nationwide overnight
courier service, in each case addressed to the Company at Vice President, Human
Resources, Banyan Systems Incorporated, 120 Flanders Road, P.O. Box 5013,
Westboro, Massachusetts 01581-5013, to the Participant at 30 Allen Circle,
Boxford, Massachusetts  01921 and to you at Clerk, Banyan Systems Incorporated,
120 Flanders Road, P.O. Box 5013, Westboro, Massachusetts 01581-5013 (or to such
other address as a party may have furnished to the other parties in writing 

                                      A-3
<PAGE>
 
in accordance herewith). Any such notice, instruction or communication shall be
deemed to have been delivered five business days after it is sent by registered
or certified mail, return receipt requested, postage prepaid, or one business
day after it is sent via a reputable nationwide overnight courier service. Any
party may give any notice, instruction or other communication hereunder using
any other means, but no such notice, instruction or other communication shall be
deemed to have been duly delivered unless and until it actually is received by
the party for whom it is intended.

     6.   Miscellaneous.
          ------------- 

     (a)  By signing these Joint Escrow Instructions, you become a party hereto
only for the purpose of said Joint Escrow Instructions, and you do not become a
party to the Agreement.

     (b)  This instrument shall be binding upon and inure to the benefit of the
parties hereto and their respective successors and permitted assigns.

                              Very truly yours,

                              BANYAN SYSTEMS INCORPORATED


                              By: /s/ William P. Ferry
                                  --------------------
                                  Name:   William P. Ferry
                                  Title:  Chairman and
                                          Chief Executive Officer

                              HOLDER


                              /s/ Robert D. Burke
                              -------------------
                              Print Name:  Robert D. Burke


ESCROW AGENT


/s/ Richard M. Spaulding
------------------------
Print Name:    Richard M. Spaulding
Print Title:   Clerk

                                      A-4