Well, now that the classic debug output has been render obsolete by Ray Camden and Adam Podolnick's ColdFire I have finally finished the FireFox version of CF Debug Copy. To install just click the link below.
This version has one minor improvement over the IE version: if the number of question marks in the query doesn't match the number of queryparams found the copied content is left unchanged. Otherwise it should work just like the IE version.
As always let me know if you have any problems. Also, I'm thinking about moving these projects to RIAForge, I just need to figure out which license to use.
I've updated the extension to work with frames.