I have already purchased a Unity Pro license. Now, a third party publisher, that will not do ANY development, wants to buy my game (for windows) and sell it itself. Are there any limitations for this process to occur? Can the third-party publisher sell as much copies as it pleases? Or do I just hand over the game build and forget about it?
Thanks for the help!
It really just depends on the contract that you agree to, and what you and the publisher decide to do.
P.S. its good if people want to buy you're game! ;)
What you are producing with Unity and Unity pro is yours ( minus all copyrighted content/assets you might have used) and you can sell it the way you like to clients. So if they want to buy your game ready made as exe, application or web app, this is perfectly fine and the way it's done most of the time.
If the client wants to own the sources as well, then you have to be careful with copyright of scripts or thirdparty extensions used. Had this problem that a client wanted to own all the sources. You can't do that if for example you used SpriteManager or EZGUI. So be careful with how you deal with the actual sources.
But what you publish is totally fine to sell to client that will in turn sell it. Like NinjaSquirrel said, then how get paid in turn based on these sales is to be agreed between you and your client, not with Unity.