Is mp3cat (http://tomclegg.net/mp3cat) legal to include in Fedora, or does the MP3 patent / licensing come into play?
This is fine. It does not encode or decode, only validates the frames and drops anything invalid. (Some of the included scripts depend on packages that we could not include in Fedora, such as "lame", so please be careful not to package those in Fedora, but the core mp3cat bits are fine.) Lifting FE-Legal.
Thanks for the feedback, I'll go ahead and package it now.