To be honest, under Fair Use, we probably could hold a kickstarter for it if we really wanted to, without permission from the Warriors copyright holders. However, we're going to avoid doing so just in case.
Moonrise uses the main concept of Warriors, but there are so many changes to it that it could be, under Fair Use, be considered a parody. Fair Use states that parts of a copyrighted work may be used in another work if it is transformative, used for educational purposes, research purposes, criticism purposes, or parody.
Moonrise falls under the 'transformative' category here- for one, it is a game rather than books.
Secondly, none of the Warriors Clans are used within Moonrise. Instead, we use our own, much different Clans with no relation to the books.
No characters from the books exist in MR, making it even more different. Along with this, the concept of StarClan is different as well- it is led by the founders as 'Gods' of sorts. Who goes to Dark Forest or StarClan is decided upon by them, rather than some random StarClan cat with a dislike for someone.(See: Bluestar and Thistleclaw)
Moonrise, although a game based heavily around "Warriors", has enough differences to qualify under fair use.
Let me use an example here(thanks fangie for ur obsession with SP that led me to find this lmao):
South Park, at one point, parodied a song called "What what in the butt".(lol) It was basically the same thing, but animated and using Butters to sing it. The song creators sued South Park over this, but South Park actually won, since it qualified under Fair Use. And South Park made money off of the episode!
Point being; Moonrise has enough differences from canon Warriors to qualify under Fair Use, whether we held a Kickstarter(monetization) for it or not. (As it turns out, under Fair Use, it actually doesn't matter if money is made or not.)
We're not going to go with a Kickstarter at this point, but it wouldn't be illegal to do so.
As it also is not illegal to make the game itself, and yes, it will be multiplayer. If it comes down to it and we cannot afford to host multiplayer servers, and we /have/ to hold a fundraiser, then we will with this same Fair Use explanation.
I don't think we'll need it, however.