FOURTH LOAN MODIFICATION AGREEMENT
This Fourth Loan Modification Agreement (this “Loan Modification Agreement’) is entered into as of
September 30, 2003, by and between SILICON VALLEY BANK , a California-chartered bank, with its
principal place of business at 3003 Tasman Drive, Santa Clara, California 95054 and with a loan production
office located at One Newton Executive Park, Suite 200, 2221 W Washington Street, Newton, Massachusetts
02462, doing business under the name “Silicon Valley East” (“Bank”) and (i) IBASIS, INC. , a Delaware
corporation with its chief executive office located at 20 Second Avenue, Burlington, Massachusetts 01803 and
(ii) IBASIS GLOBAL, INC. , Delaware corporation with its chief executive office located at 20 Second
Avenue, Burlington, Massachusetts 01803 (jointly and severally, individually and collectively, “Borrower”).
1. DESCRIPTION OF EXISTING INDEBTEDNESS AND OBLIGATIONS . Among other
indebtedness and obligations which may be owing by Borrower to Bank, Borrower is indebted to Bank pursuant
to a loan arrangement dated as of December 30, 2002, evidenced by, among other documents, a certain Loan
and Security Agreement dated as of December 30, 2002 between Borrower and Bank, as amended by a certain
First Loan Modification Agreement dated as of January 30, 2003, a certain Second Loan Modification
Agreement entered into as of February 27, 2003, and a certain Third Loan Modification Agreement dated as of
June, 2003 (as amended, the “Loan Agreement”). Capitalized terms used but not otherwise defined herein shall
have the same meaning as in the Loan Agreement.
2. DESCRIPTION OF COLLATERAL . Repayment of the Obligations is secured by the Collateral as
described in the Loan Agreement and certain Intellectual Property Security Agreements each dated December
30, 2002 (together with any other collateral security granted to Bank, the “Security Documents”).