id3v2 is a powerful command line tool for editing MP3 ID3 tags. Getting it to compile on Windows under Cygwin, though, took a bit of effort.
For the convenience of others, here is id3v2 0.1.12 compiled under Cygwin. It depends upon Cygwin and Cygwin’s zlib package.
Could you make your source code changes to id3v2 available?
I don’t have a patch for id3v2 but I do have one for id3 v0.78, see at pastebin.
cheers…ank