I, personally, think the forbidden four aren't only about the legal sensitivities the bloodthirsty lawyers are looking for, but should be more of a level of respect in terms of fan adaptations.
Their unreleased items are incomplete, and thus, not the level of quality the Project M team would want. Rightfully so, the members of the team aren't exactly proud of the broken characters and costumes. An example, someone made a reskin of Awakening Roy, and my Nanobuddy was very offended by it. It made me sad.
Another thing is that the leaked content wasn't released out of enjoyment, but spite. A dark worm from a pit was the one who released them, one without a care for the other development team .He doesn't deserve the praise he's been getting as a result.
That's just the way I view it anywho.