Correction

debian-legal serves as a discussion mailing list, not as a place were decisions are being made. The decision on whether something is free enough to be distributed in Debian main (vs. non-free, or no distribution at all) is taken by the ftp-master team.

I don't know about the specifics on this case, I do know however that fonts-liberation (previously known as ttf-liberation) is part of Debian for quite some time and is even in the current stable release (squeeze):
http://packages.debian.org/search?keywords=liberation