I had the same exact idea some years back (i.e., recording myself using Jamey Aebersold tracks as my backing band) and contacted the Aebersold company to find out about the legalities. They told me in no uncertain terms that using their tracks for any recordings that might be released to the public was forbidden. After thinking about it, I didn't really blame them, as this could lead to a prickly situation where some of the world-class jazz artists who record the Aebersold stuff could find themselves listed as "sidemen" on recordings by very amateurish players.

Of course, if you use their tracks, don't make a fuss about it, and your playing is not an embarrassment, I'm not sure how much motivation they'd have to do anything about it.

That all said, I join in the vote to use the RealTracks. They should work fine for straightforward rhythm section backing. If you need something with a lot of subtlety, dynamics, and interplay, like Wayne Shorter's stuff or early Wynton Marsalis, that would be more of a challenge.