Derivative work, licensing question

[Aspra Flavius Adrian]

Hello folks. I'm attempting to write a GPLed library and I'm concerned
about eventual licensing issues regarding the files which do not state
under which licence they are published, particularily
libpurple/protocols/yahoo/yahoo_auth.*.
Are those files GPLed too?
If not, what's the licence, and what should I add in the file headers,
beside a note stating their origin?

Regards
--
Flavius