Document:

<PAGE>

                                                                    Exhibit 10.1

                             SAI (IRELAND) LIMITED

                                    - and -

                               CLARUS CORPORATION

                            PATENT LICENCE AGREEMENT
                            ------------------------

                           BRIAN O'DONNELL & PARTNERS
                                   Solicitors
                               62, Merrion Square
                                    Dublin 2
<PAGE>

THIS AGREEMENT is made on the      day of           2000

BETWEEN:

                             SAI (IRELAND) LIMITED
                 of SAI House, The National Technological Park
         Limerick, Ireland (hereinafter referred to as the Licensor):

                                    - and -

                              CLARUS CORPORATION
                              Of Suwanee, Georgia
                  (hereinafter referred to as the Licensee).

WHEREAS:

A.   The Licensor is the registered owner of the Patents (as hereinafter
     defined) set out in the First Schedule hereto.

B.   The Licensor has agreed with the Licensee to grant to the Licensee a non-
     exclusive licence throughout the United States in respect of such Patents.

NOW THIS AGREEMENT WITNESSETH:-

                        SECTION 1.0 - INTERPRETATION
                        ------------------------------

1.1  Definitions
     -----------
     In this Agreement the following words and expressions shall have the
     following meanings:-

     (a)  "Business Day", a day on which banks in Dublin are open for business.

     (b)  "Improvements", all improvements, modifications or adaptations to the
          Patents or any of them which might reasonably be of commercial
          interest to the Licensee and which may be made, developed or acquired
          by the Licensor at any time following the execution of this Agreement.

     (c)  "Invention", the claimed subject matter of the Patents.
<PAGE>

     (d)  "Licence Payment", amounts payable in US dollars in accordance with
          the Third Schedule.

     (e)  "Patents", the patents set forth in the First Schedule, any
          corresponding patent application to be filed based on such patents,
          and all patents and other rights derived therefrom.

     (f)  "Products", all products incorporating the Patents.

1.2  Further Definitions

(a)  Any reference to any provision of any legislation shall include any
     modification, re-enactment or extension thereof;

(b)  Words such as "hereunder", "hereto", "hereof", and  "herein" and other
     words commencing with "here" shall unless the context clearly indicates to
     the contrary refer to the whole of this Agreement and not to any particular
     section or clause thereof;

(c)  Save as otherwise provided herein any reference to a clause, paragraph or
     sub-paragraph shall be a reference to a clause, paragraph or sub-paragraph
     (as the case may be) of this Agreement and any reference in a clause to a
     paragraph or sub-paragraph shall be a reference to a paragraph or sub-
     paragraph of the clause or paragraph in which the reference is contained
     unless it appears from the context that a reference to some other provision
     is intended.

1.3  Headings and Captions

     The headings in this Agreement are inserted for convenience of reference
     only and shall not be considered a part of or affect the construction or
     interpretation of this Agreement.

                             SECTION 2.0 - GRANT
                             -------------------

2.1  Grant
     -----

     In consideration of the payments set forth in Section 5 hereof, the
     Licensor hereby grants, to the Licensee, an irrevocable non exclusive
     licence and authority to use the Patents and any Improvements in the United
     States in any manner it deems fit subject to the terms and conditions of
     this Agreement, and the Licensee hereby accepts such grant.

2.2  Formal Licence
     --------------

     The parties hereby agree to execute a formal licence agreement in a form
     appropriate for each jurisdiction in respect of which the Patents are in
     force for the purpose of registering any patent licence granted pursuant to
     Section 2.1 above.  Any such formal licence agreement shall operate subject
     to the terms of this Agreement.
<PAGE>

                     SECTION 3.0 - CONCERNING THE PATENTS
                     ------------------------------------

3.1  Patent Fees
     -------------

     The Licensor shall remain responsible for the payment of all filing,
     prosecution, renewal and maintenance fees in respect of the Patents.

3.2  Infringement
     --------------

     The Licensor shall (and the Licensee may) take all proper steps to help
     maintain the validity and enforceability of the Patents, but neither party
     shall be obliged to take proceedings against any infringer of any of the
     Patents except that the Licensee shall take proceedings on the instructions
     of the Licensor if it is indemnified against the costs of so doing. Each
     party will notify the other of any infringement which comes to its notice
     and all questions on whether action shall be taken against an infringer
     shall be decided after taking into account:-

     (a)  the seriousness of the infringement;

     (b)  the strength of the Patent infringed;

     (c)  the importance of the Patent infringed;

     (d)  the expected costs of proceedings;

     (e)  the difficulty of obtaining the necessary evidence to support the
          proceedings;

     (f)  any opinion of counsel which may have been obtained by either party.

3.3  Warranty
     ----------

     The Licensor hereby warrants that:-

     (a)  that there are no other patents owned by it based on the Invention;
          and

     (b)  to the best of the Licensor's knowledge and belief the exercise of the
          rights granted or to be granted to the Licensee hereunder will not
          result in the infringement of valid patents or other rights of third
          parties; and

     (c)  save as set out in the Second Schedule hereto no other licence is in
          place in respect of the Patents at the date hereof which has not been
          cancelled or terminated.
<PAGE>

3.4  Improvements
     ------------

     The Licensor shall forthwith disclose to the Licensee in such detail as the
     Licensee may reasonably require all Improvements. Any such Improvements
     shall be deemed to thenceforth form part of the Patents hereby licensed and
     the terms hereof (including the right of the Licensee to grant sub-
     licences) shall thenceforth apply to such Improvements as if they formed
     part of the Patents as defined herein.

                            SECTION 4.0 - DURATION
                            ----------------------

4.1  Term
     ----

     This Agreement shall remain in force for a term of seven (7) years from the
     date hereof.

                      SECTION 5.0 - ANCILLARY PROVISIONS
                      ----------------------------------

5.1  Payment of Licence Fee
     ----------------------

     The Licensee's authority to use the Patents is subject to the receipt of
     the Licence Payments by Licensee to Licensor in accordance herewith. The
     parties agree that the Licensee shall make an advance payment to the
     Licensor equal to the net present value of the future payment obligations
     under the Payment Schedule attached as the Third Schedule hereto, upon
     which payment the Licence shall be fully paid and no other licence fee
     payments shall be due hereunder. The parties agree that on the date hereof,
     the net present value of all the payments due hereunder (calculated at an
     agreed upon discount rate of 6.98172% per annum) during the term of this
     Licence shall be $15,000,000.

5.2  Successors
     ----------

     This Agreement shall be binding upon and inure to the benefit of the
     parties hereto and their respective successors and assigns.

5.3  Sub-Licences
     ------------

     The Licensee shall have the right to grant sub-licences of the Patents
     without any prior reference to the Licensor. The terms of such sub-licences
     shall not be inconsistent with the obligations of the Licensee hereunder.

5.4  Assignment
     ----------

     The Licensee shall have the right to assign the benefit of the licence at
     any time (including without prejudice where it enters into liquidation or
     receivership) to any other party to whom the provisions of this clause
     shall apply mutatis mutandis.

5.5  Markings
     --------

     The Licensee shall comply with all marking obligations required by law in
     the countries covered by this Agreement and as appropriate mark the
     Products "Patent No.   " or "Patent Pending" or abbreviations thereof or
     similar words required or permitted by law.

<PAGE>

5.6  Proceedings
     -----------

     (a)  If any infringement action, claims or proceedings of any kind are
          threatened or commenced by a third party against either the Licensee
          or against the Licensor because of the Licensee's exploitation of the
          rights granted under this Agreement or its manufacture, distribution
          and servicing of the Products or on the ground that the Products
          infringe any registered design or patent monopoly right vested in such
          third party, then the party so threatened or sued shall inform the
          other forthwith in reasonable detail and the matter shall be referred
          to leading patent counsel (well versed in the laws of the country in
          which such matter will be determined) for the purpose of obtaining his
          advice on whether a defence or a threatened action will have a
          reasonable chance of a successful outcome and whether there are any
          circumstances making it imprudent to defend or commence proceedings.

     (b)  If the Licensee only shall decide that such action, claim or
          proceedings shall be defended, the Licensee shall bear the whole costs
          thereof including any damages and costs awarded against it in favour
          of such third party, and shall from time to time if requested notify
          the Licensor of the progress thereof. At the request of the Licensor,
          the Licensee may permit the Licensor to intervene or otherwise appear
          in or in connection with any such action, claim or proceedings
          personally or through Counsel selected by the Licensor, at the sole
          expense of the Licensor provided that nothing contained herein shall
          preclude the Licensor from defending such action, claim or proceedings
          where the Licensee declines to do so.

5.7  Notices
     -------

     Any notice or other communication required or permitted to be given
     hereunder shall be in writing and shall be deemed to have been duly given
     if delivered by hand against receipt of the addressee or his duly
     authorised agent or if sent by prepaid registered post addressed to the
     party to whom it is addressed at the address set out for such party herein
     or if sent by telefax to the party to whom such notice is to be given (or
     such other address or telefax number as he may from time to time designate
     in writing to all other parties hereto in accordance with the provisions
     hereof and any such notice shall be deemed to have been given if delivered
     at the time of delivery and if sent by pre-paid registered post as
     aforesaid twenty four hours after the same shall have been posted).

5.8  Variations
     ----------

     No variation or amendment of this Agreement shall bind either party unless
     made in writing and agreed to in writing by duly authorised officers of
     both parties.

5.9  Unenforceable Provision
     -----------------------

     If any provision of this Agreement is agreed by the parties to be illegal,
     void or unenforceable under any law that is applicable hereto or if any
     court of competent jurisdiction in a final decision so determines, this
     Agreement shall continue in force
<PAGE>

     save that such provision shall be deemed to be excised herefrom with effect
     from the date of such agreement or decision or such earlier date as the
     parties may agree.

5.10 Waiver
     ------

     A waiver by any party hereto of any breach by any party hereto of any of
     the terms provisions or conditions of this Agreement or the acquiescence of
     a party hereto in any act (whether of commission or omission) which but for
     such acquiescence would be a breach as aforesaid shall not constitute a
     general waiver of such term provision or condition or of any subsequent act
     contrary thereto.

5.11 Governing Law
     -------------

     This Agreement shall in all respects (including the formation thereof and
     performance thereunder) be governed by and construed in accordance with and
     governed by the laws of the Republic of Ireland and the parties hereto
     submit to the jurisdiction of the Courts of the Republic of Ireland, in
     addition to the courts of the United States.
<PAGE>

                                FIRST SCHEDULE
                                --------------

                                  The Patents
                                  -----------

                 "An inter-computer communications apparatus"

                            S.A.I. Ireland Limited
<TABLE>
<CAPTION>

Country                Application No:           Filing Date   Remarks             Ref
<S>                    <C>                       <C>           <C>                 <C>
Ireland                94 09 31                  29.11.94      Patent Granted      30339IE
                       (Patent No. 75.204)

Ireland                S94 0930                  29.11.94      Patent Granted      30339IES
Short Term             (Patent No. S63,019)

United King            9424473.8                 03.12.94      Patent Granted      30339GB
                       (Patent No. 2295699)

Belgium                09401187                  30.12.94      Patent Granted      30339BES
                       (Patent No. 1007202A6)

</TABLE>
<PAGE>

                                SECOND SCHEDULE
                                ---------------

 Existing Patent Licences Granted To Software Architects International Limited
 -----------------------------------------------------------------------------

Patent Licence between SAI (Ireland) Limited and Software Architects
International Limited (operative date 29 November 1994)

Letter SAI (Ireland) Limited to Software Architects International Limited dated
     28 November 1999 confirming extension of Patent Licence for 5 years.
<PAGE>

                                 THIRD SCHEDULE
                                 --------------

                              LICENSE FEE PAYMENTS

Date of Payment             Amount of Payment
June 1, 2000                US$2,600,000
June 1, 2001                US$2,600,000
June 1, 2002                US$2,600,000
June 1, 2003                US$2,600,000
June 1, 2004                US$2,600,000
June 1, 2005                US$2,600,000
June 1, 2006                US$2,600,000
<PAGE>

PRESENT when the common seal
of SAI (Ireland) Limited
was affixed hereto:-

By:   /s/ Richard M. O'Donnell
   ---------------------------
Name and Title: Richard M. O'Donnell, Director
                ------------------------------

PRESENT when the common seal
of Clarus Corporation.
was affixed hereto:-

CLARUS CORPORATION

By: /s/ Mark D. Gagne
   ------------------
   Mark D. Gagne, Chief Operating Officer/Chief
   Financial Officer<PAGE>

                                                                     EXHIBIT 4.9

                              SECURITY AGREEMENT

      This Security Agreement is made as of March 13, 2000 between
CarsDirect.com, Inc., a California corporation ("Pledgee") and Christine Bucklin
("Pledgor").

                                   Recitals
                                   --------

      Pursuant to Pledgor's election to purchase Shares under the Option
Agreement dated August 3, 1999 (the "Option"), between Pledgor and Bill Gross'
idealab! ("BGIL") under BGIL's 1999 Stock Plan, and Pledgor's election under the
terms of the Option to pay for such shares with his promissory note (the
"Note"), Pledgor has purchased 20,000 shares of BGIL's Common Stock (the
"Shares") at a price of $12.75 per share, for a total purchase price of
$255,000. The Note and obligations thereunder are as set forth in Exhibit A
                                                                  ---------
to this Security Agreement.

     NOW, THEREFORE, it is agreed as follows:

     1. Creation and Description of Security Interest. In consideration of the
        ---------------------------------------------
transfer of the Shares to Pledgor under the Option Agreement, Pledgor, pursuant
to the California Corporations Code, hereby pledges all of such Shares (herein
sometimes referred to as the "Collateral") represented by certificate number
CS-____, duly endorsed in blank or with executed stock powers, and herewith
delivers said certificate to the Secretary of Pledgee ("Pledgeholder"), who
shall hold said certificate subject to the terms and conditions of this Security
Agreement.

     The pledged stock (together with an executed blank stock assignment for
use in transferring all or a portion of the Shares to Pledgee if, as and when
required pursuant to this Security Agreement) shall be held by the Pledgeholder
as security for the repayment of the Note, and any extensions or renewals
thereof, to be executed by Pledgor pursuant to the terms of the Option, and the
Pledgeholder shall not encumber or dispose of such Shares except in accordance
with the provisions of this Security Agreement.

     2. Pledgor's Representations and Covenants. To induce Pledgee to enter into
        ---------------------------------------
this Security Agreement, Pledgor represents and covenants to Pledgee, its
successors and assigns, as follows:

            (a) Payment of indebtedness. Pledgor will pay the principal sum of
                -----------------------
the Note secured hereby, together with interest thereon, at the time and in the
manner provided in the Note.

            (b) Encumbrances. The Shares are free of all other encumbrances,
                ------------
defenses and liens, and Pledgor will not further encumber the Shares without the
prior written consent of Pledgee.

            (c) Margin Regulations. In the event that Pledgee's Common Stock is
                ------------------
now or later becomes margin-listed by the Federal Reserve Board and Pledgee is
classified as a "lender" within the meaning of the regulations under Part 207 of
Title 12 of the Code of Federal Regulations ("Regulation G"), Pledgor agrees to
cooperate with Pledgee in making any amendments to the Note or providing any
additional collateral as may be necessary to comply with such regulations.

     3. Voting Rights. During the term of this pledge and so long as all
        -------------
payments of principal and interest are made as they become due under the terms
of the Note, Pledgor shall have the right to vote all of the Shares pledged
hereunder.

     4. Stock Adjustments. In the event that during the term of the pledge any
        -----------------
stock dividend, reclassification, readjustment or other changes are declared or
made in the capital structure of Pledgee, all

                                      -2-
<PAGE>

new, substituted and additional shares or other securities issued by reason of
any such change shall be delivered to and held by the Pledgee under the terms of
this Security Agreement in the same manner as the Shares originally pledged
hereunder. In the event of substitution of such securities, Pledgor, Pledgee and
Pledgeholder shall cooperate and execute such documents as are reasonable so as
to provide for the substitution of such Collateral and, upon such substitution,
references to "Shares" in this Security Agreement shall include the substituted
shares of capital stock of Pledgor as a result thereof.

     5.   Options and Rights.  In the event that, during the term of this
          ------------------
pledge, subscription Options or other rights or options shall be issued in
connection the pledged Shares, such rights, Options and options shall be the
property of Pledgor and, if exercised by Pledgor, all new stock or other
securities so acquired by Pledgor as it relates to the pledged Shares then held
by Pledgeholder shall be immediately delivered to Pledgeholder, to be held under
the terms of this Security Agreement in the same manner as the Shares pledged.

     6.   Default.  Pledgor shall be deemed to be in default of the Note and of
          -------
this Security Agreement in the event:

          (a) Payment of principal or interest on the Note shall be delinquent
for a period of 10 days or more; or

          (b) Pledgor fails to perform any of the covenants set forth in the
Option or contained in this Security Agreement for a period of 10 days after
written notice thereof from Pledgee.

     In the case of an event of Default, as set forth above, Pledgee shall have
the right to accelerate payment of the Note upon notice to Pledgor, and Pledgee
shall thereafter be entitled to pursue its remedies under the California
Corporations Code.

     7.   Release of Collateral.  Subject to any applicable contrary rules under
          ---------------------
Regulation G, there shall be released from this pledge a portion of the pledged
Shares held by Pledgeholder hereunder upon payments of the principal of the
Note. The number of the pledged Shares which shall be released shall be that
number of full Shares which bears the same proportion to the initial number of
Shares pledged hereunder as the payment of principal bears to the initial full
principal amount of the Note.

     8.   Withdrawal or Substitution of Collateral.  Pledgor shall not sell,
          ----------------------------------------
withdraw, pledge, substitute or otherwise dispose of all or any part of the
Collateral without the prior written consent of Pledgee.

     9.   Term.  The within pledge of Shares shall continue until the payment of
          ----
all indebtedness secured hereby, at which time the remaining pledged stock shall
be promptly delivered to Pledgor, subject to the provisions for prior release of
a portion of the Collateral as provided in paragraph 7 above.

     10.  Insolvency.  Pledgor agrees that if a bankruptcy or insolvency
          ----------
proceeding is instituted by or against it, or if a receiver is appointed for the
property of Pledgor, or if Pledgor makes an assignment for the benefit of
creditors, the entire amount unpaid on the Note shall become immediately due and
payable, and Pledgee may proceed as provided in the case of default.

     11.  Pledgeholder Liability. In the absence of willful or gross negligence,
          ----------------------
Pledgeholder shall not be liable to any party for any of his acts, or omissions
to act, as Pledgeholder.

     12.  Invalidity of Particular Provisions. Pledgor and Pledgee agree that
          -----------------------------------
the enforceability or invalidity of any provision or provisions of this Security
Agreement shall not render any other provision or provisions herein contained
unenforceable or invalid.

                                      -3-
<PAGE>

     13.  Successors or Assigns.  Pledgor and Pledgee agree that all of the
          ---------------------
terms of this Security Agreement shall be binding on their respective successors
and assigns, and that the term "Pledgor" and the term "Pledgee" as used herein
shall be deemed to include, for all purposes, the respective designees,
successors, assigns, heirs, executors and administrators.

     14.  Governing Law.  This Security Agreement shall be interpreted and
          -------------
governed under the internal substantive laws, but not the choice of law rules,
of California.

                                      -4-
<PAGE>

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

"PLEDGOR"                                /s/ Christine B. Bucklin
                                         --------------------------------------
                                         Signature

                                         Christine B. Bucklin
                                         --------------------------------------
                                         Print Name

Address:                                 608 30th Street
                                         --------------------------------------

                                         Manhattan Beach, CA 90266
                                         --------------------------------------

"PLEDGEE"                                CARSDIRECT.COM, INC.
                                         a Delaware corporation

                                         /s/ Robert N. Brisco
                                         --------------------------------------
                                         Signature

                                         Robert N. Brisco
                                         --------------------------------------
                                         Print Name

                                         CEO
                                         --------------------------------------
                                         Title

"PLEDGEHOLDER"                           /s/ Frederick G. Silney
                                         --------------------------------------
                                         Secretary of
                                         CarsDirect.com, Inc.

                                      -5-
<PAGE>

                                   EXHIBIT A
                                   ---------

                                     NOTE

$255,000                                                         Culver City, CA

                                                                  March 13, 2000

        FOR VALUE RECEIVED, Christine Bucklin (the "Obligor") promises to pay to
CarsDirect.com, Inc., a Delaware corporation (the "Company"), or order, the
principal sum of Two Hundred Fifty Five Thousand Dollars ($255,000), together
with interest on the unpaid principal hereof from the date hereof at the rate of
seven percent (7%) per annum, compounded semiannually.

        1.      Subject to the terms and conditions of Section 2, all principal
and/or interest are due on March 13, 2005. Payment of principal and interest
shall be made in lawful money of the United States of America.

        2.      Twelve (12) months after the date Obligor ceases to be a
service provider (i.e. an employee, director or consultant) for the Company,
payment for all outstanding principal under this Note shall be due and payable.

        3.      Except as set forth above, the Obligor may not prepay the
principal or interest on this Note without the prior written consent of the
Company.

        4.      This Note is secured in part by a pledge of 20,000 shares of
Bill Gross' idealab! Common Stock under the terms of a Security Agreement of
even date herewith and is subject to all provisions thereof.

        5.      The holder of this Note shall have full recourse against the
undersigned, and shall not be required to proceed against the collateral
securing this Note in the event of default.

        6.      Should any action be instituted for the collection of this Note,
the reasonable costs and attorneys' fees therein of the holder shall be paid by
the undersigned.

                                                /s/ Christine B. Bucklin
                                                ------------------------
                                                Christine Bucklin
<PAGE>

                                   EXHIBIT B
                                   ---------

                     ASSIGNMENT SEPARATE FROM CERTIFICATE

     FOR VALUE RECEIVED I, Christine Bucklin, hereby sell, assign and transfer
unto CarsDirect.com, Inc. (20,000) shares of the Common Stock of Bill Gross'
idealab! standing in my name of the books of said corporation represented by
Certificate No. C-____ herewith and do hereby irrevocably constitute and appoint
__________________________ to transfer the said stock on the books of the within
named corporation with full power of substitution in the premises.

     This Stock Assignment may be used only in accordance with the Security
Agreement between CarsDirect.com, Inc. and the undersigned dated March 13, 2000.

Dated:                                 Signature:  /s/ Christine Bucklin
                                                 -------------------------------

INSTRUCTIONS: Please do not fill in any blanks other than the signature line.
The purpose of this assignment is to enable the Company to exercise its
"repurchase option," as set forth in the Agreement, without requiring
additional signatures on the part of the Purchaser.

                                      -2-

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