There's no problem releasing doujinshi like this (and we've also done so with Cure Assort). Doujinshi are one of the things we plan to bring back now that we're working with the artists. US law allows for works based on existing properties like this as it's all covered under parody, it can just be a headache at times.
Remember we publish everything without discrimination, we do not favor certain genres ahead of others. Ironically there are a lot of subscribers that think we publish too much vanilla and want to see more things like this, it goes both ways. That's why we'll publish everything, and sometimes it will be something you like, sometimes it won't. And hopefully sometimes you'll start liking something new or discover an artist you had no interest in before!
If you think that's the case just send us an email and we're happy to give you a refund! This book has a lot of chapters like this one. It's not your typical hentai.