Yeah, they do have a dedicated built-in base. That'll help, plus it's a tiered membership where you have to go the next level up for commenting privileges and I suspect a lot of readers will choose that option. Deadspin was the rare site where it was actually worth it to skim through the comments; there was some legitimately funny stuff there.
As to the non-competes, I guess it could be. A lot of these guys were freelancing, and I don't know how they would have pulled that off unless the non-compete explicitly barred them from starting a rival website but not from contracting with other publishers. Plus one of the writers said in an interview that they've been sitting on this since December. You'd think that would be a statement that could get them in trouble since it's basically a public admission that this had been in the works since almost immediately after the walkout. But I don't know - I've never even seen a non compete agreement, let alone signed one.