There has been some discussion of the license used in the XIFF library. XIFF is an Actionscript 3 library for XMPP chat.
As I have no comment system on my site, now or never, I ask all people using this library to take part in the discussion at the Igniterealtime community forums. There is also an issue filed for the subject.
There has been a lot of discussion of this matter at the FFmpeg developers mailing list as well.
Update 21/08/2009: As of revision 11193, XIFF uses Apache License v2.