If some dispute arises from any service contract between 2 individuals the plaintiff shall bear a lot of fees because he needs to pay for drafting of claim and schedules, translation and attendance of judgments. Certainly you are entitled to reward these costs from the defendant (icstor) but success is dependent. In all cases legal costs for such litigation exceed the price of writing services regarding porn games. Obviously they entered into gentleman agreement for cooperation.
lol the dude's a lawyer. Even if he isn't a litigation expert, suing should be much less difficult and expensive for him than for the average person. And as mentioned, as long as there's enough money involved - which, looking at the Patreon numbers posted in this thread, there is - such costs start becoming negligible.
It still depends on the contents of the agreement.
A gentlemen's agreement can still be legally valid. It's difficult for me to imagine a legal professional allowing/causing such an agreement to come into existence under terms and conditions that are
this heavily skewed against their favor. Especially with the amounts of dough involved.
And why would ICSTOR? Why would he endanger his wealth and income by neglecting to ensure that the proper licenses are in place for his cash cow? Without a license/IP transfer re: Onyxdime's writing, he'd expose himself and his collected Patreon wealth to easy-af cookie-cutter IP infringement litigation from Onyxdime. Sure, litigating over incest porn you wrote is embarrassing, but that shit goes out the window for most if there's enough money involved.
EDIT: the EU also has best-seller rights to protect authors. Don't know for sure how that would work after the Brexit but I think ICSTOR is in the EU and the UK likely has some equivalent.