It's one of the things that stunk with Inglis. If you read about what went on in Melbourne, the players were just used to snapping their fingers and getting whatever they wanted during contract negotiations, even if it was illegal / outside the cap. Obviously he thought that demanding his new club pay for his legal fees was a reasonable expectation. But to do so would have to have been included in the cap. Hence why Souths got Mundine to do it.
It's a grey one. You could argue that Mundine only did it so that he'd sign with Souths, and technically that is not allowed as 3rd party payments are not allowed to be conditional with playing for a certain club. But it's not actually a payment to Inglis, it's a payment to the legal team. Messy.
On top of that, Souths tried to sign him for $190k under the cap, with the majority of his deal coming from 3rd party stuff. The NRL however investigated and found that a heap of it was conditional to him playing for Souths (like a deal with a Redfern car dealership) and eventually they were forced to have $650k of his contract included in the cap. I think this is what
@Big Pete was alluding to, in that he signed a deal that was not yet approved by the NRL, whereas Brisbane were spending the time getting it all checked and approved first.