Third, he can't be traded to San Antonio again this season, as they already traded for him once and cut him.
I actually don't think this is correct, but I'm not positive. The rules are you can't sign a player who was cut
after you traded him, so Atlanta couldn't have re-signed him after the trade (but they could now that we've signed him). Also, you can't re-acquire a player in a trade that you
traded away in the same season, and the offseason counts as part of this season for purposes of this rule, so we couldn't trade him to Atlanta (I think -- maybe we could since we signed him as a free agent.)
But I don't think there are rules about acquiring someone via trade whom you cut, assuming you didn't stretch the contract, which I don't think the Spurs did in this case, or reduce the value via a buyout (again, I don't think the Spurs did this, since the contract wasn't fully guaranteed).
I'm pretty sure the Spurs are on the table, but I might be wrong, because the rules are confusing around this issue.