AS MusicBrainz
I WANT the BBC to release MP::ProcessSize for public use
SO THAT I can use it (in musicbrainz-server etc) without having to write it myself

The BBC has a module (written by djce and based on Apache::SizeLimit) called MP::ProcessSize, that would be useful to MusicBrainz.

Release to github, cpan, or whatever. Somewhere where MusicBrainz can legally use it.

However: my personal guess is that it would be far quicker and more effective for MusicBrainz to re-implement it themselves, perhaps after discussion with djce.