While I love Mark Cuban, this move is clearly not just out of the "goodness of his heart". He is a savvy investor. The production company (Finnmax) was receiving the equity stake, not the sharks. He rightly felt that the clause was limiting the quality of startups trying to get on the show. Now that he's used his leverage to get rid of it, he will get better opportunities to invest in.
He also gets the benefit of now seeming more entrepreneur friendly than the other sharks, which increases he chance of participating in deals.