Well.. I can't speak for the other instructors but you should probably get permission first. It's sort of a grey area right now and kinda depends on the situation and what file you're talking about. ie, moogboog is available in 3 different versions.
The first one is maybe 500k and extremely "lofi". That one is free to be passed around (for now) as long as the copyright info (and preferably the lesson) goes with it.
The second one is about about 3MB and of better quality. That one is being sold on a CD and individually at places like iTunes and I'd prefer you get permission first before ya just give it away to somebody. (although for now, I'm letting guitartricks users access it on my own server for free)
The third one which hasn't been released yet, is the final "hifi" version and should be treated like any other copyrighted song. ie, I'm gonna be selling it so I'd prefer it if ya didn't just give it away.

As far as the lessons go tho... like I said... it's a grey area right now cause Guitartricks is eventually going to morph into a pay-per-use site. Once that happens, I think we're gonna get more stringent as to what gets passed around.