What are the requirements for getting a mod on repo?

Now I've had a mod go on the repo already, but are there specific rules or things you need to have to get a mod on the repository? I guess what I'm trying to say is what will get a mod rejected?
This might be a dumb question but I'm just asking.

 

I think one of the rules is that your mod can't have any copyrighted content, for example, car with a real life name won't get approved on the repo.

 

I also think models can't be from other games/stolen/licensed/etc