Edit: I found a few different libraries, all of course named "ID3Tag" or similar, that could make a case for a distinct tag:
- id3tag, a native Ruby library for ID3 tags
- org.blinkenlights.jid3.ID3Tag, a Java class for reading tags
- the question Compiling ID3Tag asks about cross-compiling a library which I couldn't distinctly identify
- ID3TagLib.Net, a C# library
However I think questions about these libraries might be better served by the id3 tag.