I can confirm your suspicions: there is nothing and literally everyone can come and join in the madness. SJ implemented one rule after the incident with the homophobic woman, who brought her daughter and father in law along, which in SJ's assessment of the situation made it impossible to throw them out. Same thing happened when the Nordic Weirdo workawayer brought a friend when they came to the shittoo and SJ wanted Weirdo in her bed, but the friend was impossible to keep around due to bad behavior. But she found a way to get rid of the friend anyway by demanding Nordic Weirdo to take care of that.
So, the one rule she now enforces is that no families or otherwise closely connected groups of people are allowed to come and work her shit. But that's basically it, no vetting, no background checks, no NDA to sign, just join in the magic whatever way you like with whatever you bring to the party. I suspect it's part of what she is so thrilled about anyway: the prospect of possible drama to keep boredom submerged.