OK, I just copied what seemed relevant. For the full rule, check out the link.
RULE NO. 8-OUT-OF-BOUNDS AND THROW-IN
Section I-Player The player is out-of-bounds when he touches the floor or any object on or outside a boundary. For location of a player in the air, his position is that from which he last touched the floor.
This seemed relevant because I believe the argument being made is that since Wade jumped from the front court and landed in the backcourt, it was like he caught the ball in the front court. However, this rule applies for players going out of bounds. I didn't see anything about jumping and catching a ball inbounds.
Section III-The Throw-In
e. Any ball out-of-bounds in a team's frontcourt or at the midcourt line cannot be passed into the backcourt. On all backcourt and midcourt violations, the ball shall be awarded to the opposing team at the midcourt line, and must be passed into the frontcourt.
EXCEPTION: During the last two minutes of the fourth period and/or any overtime period, the ball may be passed anywhere (frontcourt or backcourt) on the court.
That's all it says on inbounding a ball. Seems like Cuban is reaching. I see what his argument is, but the only time that it matters where a guy jumped from is when he goes out of bounds, I think.