First off, this belongs in the copyrights section, not the patents section.
I have 6 songs I wrote alone. I had help with the musical arrangements. His name is on the copyright. What does he now get? He is listed only as co-author of the musical arrangements. He should have credit, BUT has not helped financially at all and wants 40% PROFITS.
Am I screwed?
I guess potentially, depending on how you define "screwed." As a co-owner of the copyright, the other guy is certainly entitled to something, whether it be 40% of profits or something else. The law doesn't spell out exactly how co-owners of copyrights are supposed to handle these types of disputes -- but the law does say that each co-creator owns the whole copyright, see 17 USC 101 for a definition of "joint work." If you read that broadly enough, that would imply that the other guy would be entitled to half, not 40%, because he is an equal co-owner with you.
But you don't need to tell him that!
You should do now what you should have doen in the begining -- figure out shares of the profits, and write it down. Perhaps for a bit more than 40% he would be willing to sell his interest in the copyright to you, so you would own the whole copyright (although his name would still be on it as one of the creators). Or, at the very least, you can figure out an arrangement that will keep you guys relatively happy going forward. If you do try and get this arranged contractually (and you should), and the profits are in any way significant, get a lawyer to help you draft everything.
And finally, if you can't agree on anything, you may just have to let the courts decide...
