I think it was .tar.bz or something like that. I don't remember exactly. It is used for some source codes, specially for Linux. I had to add .zip at the end to be able to upload them. I try to keep the files the same way they are on the authors' pages and that's why I do not re-zip them normally. Also, there was some Mac file format which I had to rename.
When I'm able to remember which emulators use it, I'll let you know the exact extensions.
And let's hope that the spam issue is solved with the new software. Thanks for updating it Edman.