I doubt they have a patreon for this game specifically. Morenatsu is not their property, making a fan-game is one thing (a risky thing by the way because your work can be ultimately thrown into the trash if the owners of the original game decide to sue for example) but a fan-game that makes money with it is deffinitely something the original owners would fall on to stop right away. You can't just borrow someone else's project just because it was canceled and start making money with it. The legal issue can be really threatening.
I'm pretty sure they have a patreon for the other project they have though, Santa Lucia I think the name is.