Francesco Poli wrote:
Second option would require the Debian package maintainer to dig into
the source and play "seek & destroy" with all cases in which the work is
referenced as "Mozilla {thunderbird|firefox}" or in which the official
logo is used...
This seems a bit more than requiring a name change (per DFSG 4).
I should point out that changing the name of Firefox and Thunderbird is designed to be easy. Netscape does it with the suite to make Netscape, after all. There's a central branding file or two where you change the name once and it's picked up almost everywhere.
I'm not saying it's trivial, but it is true that things that make it difficult are treated as bugs, not features, and fixed.
Gerv