Entry points into a wireless network are neither infinitely available, nor free. To be sure, you can have a LOT of shortcodes available, but they're not infinite. The problem here is that the TOS with the party offering the short codes to third parties explicitly signed a contract saying they needed approval from T-Mobile for any new services they'd offer on one of the short codes they have assigned to them. They did not do so, so T-Mobile cut them off.
I'm not sure why this is a problem here.