Comment 1 for bug 965049

The Open Font Library is dependent upon Fontaine for reading the font license information.

If you actually look at PT Serif, the License reads in part:

Copyright (c) 2010 Paratype.... This Font Software is license under the Open Font License......

and includes a copy of the whole license. Fontaine is looking for a simple string and is unfortunately confused by all that text.

This bug needs to be filed upstream with Fontaine.