On 12/15/2017 at 1:33 PM, steelstrung said:By the way, what do you guys think I should do with what he already contributed to the project? Since he never signed any sort of agreement or anything I guess I am a bit concerned it could become a legal issue later.
You should be.
Each person owns their own individual contribution. In a joint work each person becomes a co-owner of the work, and once merged they are generally considered inseparable. Even if you revert their changes, that person may still be able to demand payments or block various uses. If you cannot get all the co-owners to agree, for example when licensing the product to another group or publishing the game, then the project can be legally tainted. All it takes is one disgruntled person, or one person who seems to have vanished from the earth, and your project enters a bad state.
On 12/15/2017 at 4:08 PM, steelstrung said:So deleting everything he added from the site would probably work best? It wouldn't be a crippling loss, that's for sure, but it would I suppose it complicates things
That is exactly why they become a joint owner of the work and it is usually considered inseparable.
Get with a lawyer to help you make a collaboration agreement, contracting agreement, rights assignment, or various other contract. Your lawyer can tell you the difference, and you'll need forms for each person on the project.
For the person that left, tell them there are no hard feelings, tell them that since the project needs to go on you need to make sure you still have legal rights to use what they contributed, tell them they can still claim credit for whatever they want, and perhaps even give them twenty bucks (which the rights assignment form will call "valuable consideration") in exchange for their signature.
Everyone else on the project should sign an agreement as well. They'll probably get collaboration agreements since they are still contributing on the team.