William reached out to us when you initially contacted him over your conflict with another involved party because it put him in an awkward spot as both a moderator as well as a member of the project in question. As far as I know, he has since offered you to remove the assets in dispute in the next version of the mod.
If you wish to go through the official procedure despite that - please follow these guidelines:
1. Attempt to resolve the situation with the offending party.
2. If that proves impossible, you may contact the moderation and should provide us with all the necessary information. (Description of the Problem, Description of the Attempt to Resolve, Proof of Offense, Proof of Rights to Assets, Proof of Agreements/Permissions, Other Information you deem necessary/helpful)
3. If we consider an action in conflict with our rules, we will ask the offender (modder, server owner and/or host) to rectify the situation. You should avoid unnecessarily escalating the conflict at this point.
That is to say, you should send me (since William is involved) a private message with a detailed description of the situation, which includes a list of the assets in dispute, any proof of creation you may have, any logs of any terms of collaboration that may have been there, a log of the attempt to resolve and any other information you deem helpful to a swift resolution.