Right, lets set the record straight on covers.
A cover is when you play music written by somebody else, fair enough, but the copyright that protects the printed, written, sheet music is thus:
You can cover the song and perform/distribute your cover, as long as you don't charge for it. As soon as you start charging for it, you have to pay royalties to the company that published the sheet music for the public domain.
As long as you don't actually use their sheet music, and tab/work out the chords yourself, you are not actually using ANY of their origional material, and instead your interpretation of their song, which, no matter how good you are, will never be the same as the origional, and although its technically legitamate to sell a cover, you probably still would get hounded by layers trying to make a little extra money for their clients.
On this basis, you technically can upload covers, both from the official sheet music/tabs, or your own interpretation as long as you do it non-commercially.