Another issue is that the trademark policy prohibits selling unmodified copies, http://jxself.org/mozilla_trademark.shtml. This seems significant enough to not use this package for distro releases (and probably makes the package nonfree, although this isn't discussed often).
A development build of Trisquel had Firefox with a separate JavaScript file changing the addon list, this was changed due to what Andrew wrote (and the no-selling clause).
pgpV4vX8dNGCo.pgp
Description: PGP signature
