I would have said all of this on an existing thread, but nobody ever seems to notice my replies, so I thought I'd make a post to highlight what I have discovered in my research about the subject of private server legality, and I hope to help you feel better when it comes to trying to bring Monkey Quest back!
Well, it all starts with DMCA's. A DMCA is what Nickelodeon would send to you if they want you to shut down your game. This, hopefully, would not happen anyway because Monkey Quest has been closed ages, and the rights are running out this year from what I have heard on this wiki. However, if it did, the simple answer is: Take the game down. This is the most important bit: You will not have to pay any money, go to court, or face any punishment, as long as you simply take it down. This is what a DMCA is asking you to do: Take the game down or else the aforementioned punishment will be considered. No worries as long as you just take it down. Depending on whether you had made a website for it, you could try and simply post the project and its news here on the wiki quietly, or if you don't want to risk it again, somebody else could try again. I'd sure be happy to give it a shot.
My next and final point is this. The issue of money. Private servers are only illegal and very likely to be targeted by the owners (Nickelodeon, in this case) if money is involved in any way. The only money that should be used is money that is necessary to run the game, if that was what it would ever require. Nobody should be paid for working on the game, and nobody should be paid to work on the game. This is a clear trek into illegal territory. The one thing I originally noticed with Monkey Quest Rewritten was that it took donations. This is one thing that should not be done; no money should be accepted from supporters. The owner of any server that might be created should not pay anyone to work on the game, nor should any players pay them to help work on it. Any money that might be necessary for the game should come out of the staff members' pockets.
I'm very sorry if I've come off as too blunt with you; that was not my intention. These paragraphs have simply been composed to ease your minds about creating or helping to create a Monkey Quest private server, and to give you the one important guideline that must be followed. I am a member of the community of various private servers for other closed games, such as Toontown and LEGO Universe; both already-open servers, and ones that are in active development. I took the time to ask the developers of these servers about the subject of a private server's legality, and their answers all came down to the same core points, which I have brought out here. If you have read all the way here, thank you very much. If not, I don't blame you; this is pretty long! :P Anyway, I hope this could help clear a few things up. This is Mariomania123, signing off!