You should visit http://support.wolfram.com/technotes/latestfonts.en.html
for up to date license and accept it. As of 02.12.2008 the text on that page was:

READ THIS AGREEMENT CAREFULLY BEFORE PROCEEDING. IT IS AN AGREEMENT BETWEEN
WOLFRAM RESEARCH, INC. ("WRI"), AND YOU. ACCEPTANCE OF ITS TERMS CREATES A
BINDING CONTRACT BETWEEN YOU AND WRI.

Wolfram Research, Inc. ("WRI") licenses Mathematica fonts to individual users
downloading from this site. All WRI fonts are copyright Wolfram Research, Inc.
or its vendors. All rights reserved. WRI fonts are not in the public domain.

WRI reserves the right to control all distribution of the Mathematica fonts and
does not, at this time, allow them to be widely distributed via any servers,
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transmitted to service bureaus, publishers, or other users of WRI products.
There are no restrictions on widely distributing metrics files generated from
the Mathematica fonts.

WRI does not require authors to credit Wolfram Research for the use of the
Mathematica fonts in published papers. However, such credit is appreciated.
“Mathematica fonts by Wolfram Research, Inc.” is sufficient.