<PAGE>

                                                                     EXHIBIT 4.8

                      SIXTH AMENDMENT TO CREDIT AGREEMENT,
                THIRD AMENDMENT TO PLEDGE AND SECURITY AGREEMENT,
                         LENDER'S CONSENT AND AGREEMENT

         THIS SIXTH AMENDMENT TO CREDIT AGREEMENT, THIRD AMENDMENT TO PLEDGE AND
SECURITY AGREEMENT, LENDER'S CONSENT AND AGREEMENT (this "Amendment") is dated
effective December 2, 2003, by and between TYLER TECHNOLOGIES, INC., a Delaware
corporation ("Borrower") and BANK OF TEXAS, N.A., a national banking association
("Lender").

                                   WITNESSETH:


         WHEREAS, Borrower and Lender entered into that certain Credit
Agreement, dated February 27, 2002, pursuant to which Lender made the Loan (as
therein defined) available to Borrower (as heretofore or hereafter amended, the
"Credit Agreement")(each capitalized term used herein, but not otherwise defined
shall have the same meaning given to it in the Credit Agreement); and

         WHEREAS, to secure the Loan, Borrower and Lender entered into that
certain Pledge and Security Agreement dated February 27, 2002 (as heretofore or
hereafter amended, the "Tyler Pledge Agreement") whereby Borrower pledged as
security, among other things, all of its shares of stock in its Subsidiaries;
and

         WHEREAS, the Credit Agreement currently prohibits Borrower from making
any Acquisition, other than a Permitted Acquisition, without the express written
consent of Lender; and

         WHEREAS, Borrower desires to enter into that certain Stock Purchase
Agreement dated as of December 2, 2003, whereby Borrower agrees to acquire (a)
ninety five percent (95%) of the stock of Eden Systems, Inc., a Washington
corporation ("Eden Systems"), and (b) an option to acquire the remaining five
percent (5%) of the stock of Eden Systems (collectively, the "Proposed
Acquisition"); and

         WHEREAS, pursuant to the terms of the Credit Agreement, the Proposed
Acquisition does not qualify as a Permitted Acquisition;

         WHEREAS, Borrower has requested that Lender consent to the Proposed
Acquisition; and

         WHEREAS, subject to the terms and conditions herein contained, Lender
is willing to agree to such requests.

         NOW, THEREFORE, in consideration of the covenants, conditions and
agreements hereinafter set forth, and for other good and valuable consideration,
the receipt and adequacy of which are all hereby acknowledged, Borrower and
Lender hereby covenant and agree as follows:

                               ARTICLE I - CONSENT

SECTION 1.1 CONSENT TO PURCHASE OF EDEN SYSTEMS. The Credit Agreement provides,
among other things, that, without the prior written consent of Lender, Borrower
shall make no Acquisition, other than a Permitted Acquisition. Lender hereby
consents to the Proposed Acquisition. Lender further agrees that, for all
purposes of the Loan Documents, Eden Systems shall be deemed a wholly-owned
Subsidiary of Borrower so long as 95% or more of the total voting power of the
shares of capital stock entitled to vote in the election of directors of Eden
Systems is directly or indirectly owned by Borrower or any Subsidiary

SIXTH AMENDMENT(TYLER)                                                    PAGE 1

<PAGE>


(other than the Excluded Subsidiaries). Notwithstanding anything contained
herein to the contrary, Lender's consent to the Permitted Acquisition shall be
effective as of December 1, 2003, and shall not be conditioned on any of the
conditions set forth in Section 4.1 below.

SECTION 1.2 LIMITATION ON CONSENT. The consent granted in this Amendment is
limited to the foregoing action and does not constitute a waiver of any required
consent with respect to any other action.

                             ARTICLE II - AGREEMENT

SECTION 2.1 EFFECT OF ACQUISITION ON FUTURE PERMITTED ACQUISITIONS. Lender and
Borrower hereby agree that the Acquisition consented to in this Amendment shall
not reduce the $3,000,000 limit, as set forth in subsection (a) of the
definition of "Permitted Acquisition" in the Credit Agreement, within which
Borrower can make Permitted Acquisitions.

                            ARTICLE III - AMENDMENTS

SECTION 3.1 MODIFICATION TO CREDIT AGREEMENT. As of the date of this Amendment,
the following definitions shall be amended and restated, each in its entirety,
to read as follows:

         "Existing Subsidiaries" means Cole Layer Trumble Company, a Delaware
         corporation; Eagle Computer Systems, Inc., a Delaware corporation; Eden
         Systems, Inc., a Washington corporation; FundBalance, Inc., a Delaware
         corporation; Interactive Computer Designs, Inc., a Texas corporation;
         MUNIS, Inc., a Maine corporation; and The Software Group, Inc., a Texas
         corporation, but does not include the Excluded Subsidiaries.

         "Permitted Investments" shall mean (a) obligations, with a maturity of
         less than two years, with the full faith and credit of the United
         States of America, (b) direct obligations of any state of the United
         States, or municipality therein, rated in one of the two top
         classifications by S&P or Moody's and maturing within one year from
         date of acquisition, (c) certificates of deposit, eurodollar time
         deposits or banker's acceptances, maturing within two years from date
         of acquisition, issued by (1) Lender, (2) Texas Capital Bank (Dallas,
         Texas) or (3) any United States commercial bank having capital, surplus
         and undivided profits aggregating not less than $100 million and whose
         (or whose parent corporation's) unsecured long-term debt is rated in
         one of the two top classifications by S&P or Moody's, (d) repurchase
         obligations with a term of not more than seven days for underlying
         securities of the types described in clauses (b) and (c) above entered
         into with any financial institution meeting the qualifications
         specified in clause (c) above, (e) commercial paper of any United
         States corporation with a maturity of less than 270 days from date of
         acquisition and which is rated in one of the two top classifications by
         S&P or Moody's, (f) indebtedness of any United States corporation with
         a maturity of less than 270 days from date of acquisition and which is
         (1) evidenced by bonds, notes, debentures or other instruments issued
         and authenticated under an indenture qualified under the Trust
         Indenture Act of 1939, as amended, and (2) rated in one of the two top
         classifications by S&P or Moody's, (g) investments in money market or
         mutual funds at least ninety percent (90%) of the assets


SIXTH AMENDMENT(TYLER)                                                    PAGE 2

<PAGE>


         of which constitute Dollars or investments in securities of the type
         described in clauses (a) through (f) above (without regard to
         maturities), (h) investments in money market or mutual funds (other
         than those described in clause (g) above) acquired through and
         maintained in an account with Lender or any Person controlled by,
         controlling or under common control with Lender, (i) Investments in
         wholly-owned Subsidiaries of Borrower, so long as Borrower has complied
         with the requirements of Section 9.4 with respect thereto, (j) expense
         advances to employees in the ordinary course of business for travel and
         lodging not to exceed $100,000 in the aggregate at any time
         outstanding, (k) Investments in demand deposit accounts maintained with
         FDIC member banks, (l) Investments outstanding on the date of this
         Agreement that are disclosed in Schedule 9.10, and (m) Investments in
         or for the benefit of Swan pursuant to the plan of reorganization to
         which reference is made in clause (a)(iv) of Section 6.7.

SECTION 3.2 MODIFICATION TO TYLER PLEDGE AGREEMENT. As of the date of this
Amendment, Exhibit "E" to the Tyler Pledge Agreement shall be deleted and
replaced with the Exhibit "E" attached hereto as Exhibit A.

                              ARTICLE IV - WAIVER

SECTION 4.1 WAIVER OF CONTROL AGREEMENT REQUIREMENT FOR CERTAIN PERMITTED
INVESTMENT ACCOUNTS. Lender hereby (a) waives any Default or Event of Default
that may have occurred as a result of Borrower's failure to deliver a control
agreement regarding its Permitted Investments account with Texas Capital Bank in
Dallas, Texas and its Permitted Investments accounts with affiliates of Bank of
Oklahoma, N.A., and (b) agrees that Borrower shall not be obligated to deliver
control agreements regarding its Permitted Investments account with Texas
Capital Bank in Dallas, Texas or its Permitted Investments accounts with
affiliates of Bank of Oklahoma, N.A. until such time as Borrower is directed to
do so in a written notice given to Borrower by Lender.

SECTION 4.2 LIMITATION ON WAIVER. The waiver and agreement granted in Section
4.1 of this Amendment is limited to (a) Borrower's Permitted Investments account
with Texas Capital Bank in Dallas, Texas in effect on the date of this Amendment
and (b) Borrower's Permitted Investments accounts with affiliates of Bank of
Oklahoma, N.A. in effect on the date of this Amendment, and does not constitute
a waiver of any required account control agreement with respect to any account
established by Borrower after the date of this Amendment with any financial
intermediary for the purpose of holding Collateral.

                           ARTICLE V - MISCELLANEOUS

SECTION 5.1 CONDITION TO CLOSING. As a condition to the closing of this
Amendment, Borrower shall satisfied the following conditions:

         5.1.1 Borrower shall have executed and delivered this Amendment;

         5.1.2 Borrower shall have delivered that certain Amended and Restated
Subsidiary Guaranty dated effective of even date herewith executed by the
Subsidiary Guarantors (as defined therein) to and for the benefit of Lender;

SIXTH AMENDMENT(TYLER)                                                    PAGE 3

<PAGE>



         5.1.3 Borrower shall have delivered that certain Pledge and Security
Agreement dated effective of even date herewith executed by Eden Systems to and
for the benefit of Lender;

         5.1.4 Borrower shall have delivered to Lender that certain Amended and
Restated Contribution and Indemnification Agreement executed by and between
Borrower, each Guarantor (as defined therein) and Lender;

         5.1.5 Borrower shall have delivered to Lender the original stock
certificates evidencing all of the shares of stock of Eden System purchased in
the Proposed Acquisition, together with related stock powers executed in blank
by the appropriate Person;

         5.1.6 Borrower shall have delivered to Lender an Officer's Certificate
from Eden Systems dated as of the date hereof certifying, inter alia, (A) the
Articles of Incorporation or Bylaws (or equivalent corporate documents), as
amended and in effect, of Eden Systems; (B) resolutions duly adopted by the
Board of Directors of Eden Systems authorizing the transactions contemplated
hereby; and (C) the incumbency and specimen signatures of the officers of Eden
Systems authorized to execute documents on its behalf; and

         5.1.7 Borrower shall have delivered to Lender a certificate from the
appropriate public official of the jurisdiction in which Eden Systems is
organized as to the continued existence and good standing of Eden Systems.

SECTION 5.2 FURTHER ASSURANCES. In addition to the documents identified above in
Section 4.1, Borrower also agrees to provide to Lender such other documents as
may be necessary or as may be required, in the opinion of counsel to Lender, to
effect the transactions contemplated hereby and continue the liens and/or
security interests of all other collateral instruments, as modified by this
Amendment, and such other documents and instruments as Lender reasonably may
request in connection with the modification of the Loans effected hereby.

SECTION 5.3 AUTHORIZATION TO FILE. Borrower authorizes Lender to file financing
statements without notice to Borrower, with all appropriate jurisdictions, as
Lender deems appropriate, in order to perfect or protect Lender's interest in
the Collateral.

SECTION 5.4 CONTINUING EFFECT. Except as modified and amended hereby, the Credit
Agreement and other Loan Documents are and shall remain in full force and effect
in accordance with their terms.

SECTION 5.5 PAYMENT OF EXPENSES. Borrower agrees to pay to Lender the reasonable
attorneys' fees and expenses of Lender's counsel and other expenses incurred by
Lender in connection with this Amendment.

SECTION 5.6 BINDING AGREEMENT. This Amendment shall be binding upon, and shall
inure to the benefit of, the parties' respective representatives, successors and
assigns.

SECTION 5.7 NO DEFENSES. Borrower by its execution of this Amendment, hereby
declares that it has no set-offs, counterclaims, defenses or other causes of
action against Lender arising out of the Loan, this Amendment or otherwise; and,
to the extent any such setoffs, counterclaims, defenses or other causes of
action may exist, whether known or unknown, such items are hereby waived by
Borrower.

SECTION 5.8 USURY SAVINGS CLAUSE. Notwithstanding anything to the contrary in
this Amendment, the Note or any other Loan Document, or in any other agreement
entered into in connection with the Note or securing the indebtedness evidenced
by the Note, whether now existing or hereafter arising and

SIXTH AMENDMENT(TYLER)                                                    PAGE 4

<PAGE>


whether written or oral, it is agreed that the aggregate of all interest and
other charges constituting interest, or adjudicated as constituting interest,
and contracted for, chargeable or receivable under the Note or otherwise in
connection with the Note shall under no circumstances exceed the maximum rate of
interest permitted by applicable law. In the event the maturity of the Note is
accelerated by reason of an election by the holder thereof resulting from a
default thereunder or under any other document executed as security therefor or
in connection therewith, or by voluntary prepayment by the maker, or otherwise,
then earned interest may never include more than the maximum rate of interest
permitted by applicable law. If from any circumstance any holder of any of the
Note shall ever receive interest or any other charges constituting interest, or
adjudicated as constituting interest, the amount, if any, which would exceed the
maximum rate of interest permitted by applicable law shall be applied to the
reduction of the principal amount owing on such Note or on account of any other
principal indebtedness of the maker to the holders of such Note, and not to the
payment of interest, or if such excessive interest exceeds the unpaid balance of
principal thereof and such other indebtedness, the amount of such excessive
interest that exceeds the unpaid balance of principal thereof and such other
indebtedness shall be refunded to the maker. All sums paid or agreed to be paid
to the holder of the Note for the use, forbearance or detention of the
indebtedness of the maker to the holder of such Note shall be amortized,
prorated, allocated and spread throughout the full term of such indebtedness
until payment in full for the purpose of determining the actual rate on such
indebtedness is uniform throughout the term thereof.

         The terms "maximum amount" or "maximum rate" as used in this Amendment
or the Note, or in any other agreement entered into in connection with the Note
or securing the indebtedness evidenced by the Note, whether now existing or
hereafter arising and whether written or oral, include, as to Chapter 303 of the
Texas Finance Code (and as same may be incorporated by reference in other
statutes of the State of Texas), but otherwise without limitation, that rate
based upon the "weekly ceiling"; provided, however, that this designation shall
not preclude the rate of interest contracted for, charged or received in
connection with the Loan from being governed by, or construed in accordance
with, any other state or federal law.

SECTION 5.9 COUNTERPARTS. This Amendment may be executed in several
counterparts, all of which are identical, each of which shall be deemed an
original, and all of which counterparts together shall constitute one and the
same instrument, it being understood and agreed that the signature pages may be
detached from one or more of such counterparts and combined with the signature
pages from any other counterpart in order that one or more fully executed
originals may be assembled.

SECTION 5.10 CHOICE OF LAW. THIS AMENDMENT SHALL BE GOVERNED BY, AND CONSTRUED
IN ACCORDANCE WITH, THE LAWS OF THE STATE OF TEXAS, EXCEPT TO THE EXTENT FEDERAL
LAWS PREEMPT THE LAWS OF THE STATE OF TEXAS.

SECTION 5.11 ENTIRE AGREEMENT. This Amendment, together with the other Loan
Documents, contain the entire agreements between the parties relating to the
subject matter hereof and thereof. This Amendment and the other Loan Documents
may be amended, revised, waived, discharged, released or terminated only by a
written instrument or instruments, executed by the party against which
enforcement of the amendment, revision, waiver, discharge, release or
termination is asserted. Any alleged amendment, revision, waiver, discharge,
release or termination which is not so documented shall not be effective as to
any party.

         THIS AMENDMENT AND THE OTHER LOAN DOCUMENTS REPRESENT THE FINAL
AGREEMENT BETWEEN THE PARTIES RELATED TO THE SUBJECT MATTER HEREIN CONTAINED AND
MAY NOT BE CONTRADICTED BY EVIDENCE OF PRIOR, CONTEMPORANEOUS OR SUBSEQUENT ORAL
AGREEMENTS OF THE PARTIES. THERE ARE NO UNWRITTEN ORAL AGREEMENTS BETWEEN THE
PARTIES.



SIXTH AMENDMENT(TYLER)                                                    PAGE 5

<PAGE>


         IN WITNESS WHEREOF, this Amendment is executed effective as of the date
first written above.

                                     LENDER:


                                     BANK OF TEXAS, N.A., a national banking
                                     association



                                     By:
                                        ---------------------------------------
                                           Mark Wade
                                           Senior Vice President


                                     BORROWER:


                                     TYLER TECHNOLOGIES, INC. a Delaware
                                     corporation



                                     By:
                                        ---------------------------------------
                                           Brian K. Miller,
                                           Vice President-Finance


SIXTH AMENDMENT(TYLER)                                            SIGNATURE PAGE

<PAGE>



                                    EXHIBIT A

                           List of Pledged Securities

                    (See Section 3.11 of Security Agreement)

A. STOCKS:

<Table>
<Caption>

                                                                        CERTIFICATE   NUMBER OF
ISSUER                                 SHAREHOLDER                        NUMBER       SHARES
------                                 -----------                      -----------   ---------
<S>                                    <C>                              <C>           <C>
Cole Layer Trumble Company             Tyler Technologies, Inc.              2          1,000
Eagle Computer Systems, Inc.           Tyler Technologies, Inc.              2          1,000
FundBalance, Inc.                      Tyler Technologies, Inc.              2          1,000
Interactive Computer Designs, Inc.     Tyler Technologies, Inc.              2          1,000
MUNIS, Inc.                            Tyler Technologies, Inc.             13           5000
The Software Group, Inc.               Tyler Technologies, Inc.              2          1,000
Eden Systems, Inc.                     Tyler Technologies, Inc.                        47,500
</Table>


B. BONDS:

<Table>
<Caption>

Issuer            Number            Face Amount          Coupon Rate         Maturity
------            ------            -----------          -----------         --------
<S>               <C>               <C>                  <C>                 <C>
None
</Table>

C. GOVERNMENT SECURITIES:

<Table>
<Caption>

Issuer            Number   Type     Face Amount       Coupon Rate       Maturity
------            ------   ----     -----------       -----------       --------
<S>               <C>      <C>      <C>               <C>               <C>
None
</Table>


D. OTHER SECURITIES OR OTHER INVESTMENT PROPERTY
   (CERTIFICATED AND UNCERTIFICATED):

<Table>
<Caption>

Issuer            Description of Collateral        Percentage Ownership        Interest
------            -------------------------        --------------------        --------
<S>               <C>                              <C>                         <C>
None
</Table>



EXHIBIT A - SIXTH AMENDMENT(Tyler)                                       PAGE 1