Don't worry about all the questions, when I got involved in the project I was all questions too...Just ask Joe...
It looks to me like the site is just looking out for the rights of the authors of the models that contributed to their site. They don't want people coming there, downloading the models, and then selling them without permission, or something like that.
However it looks like if you contact the author, and get their permission, then it's fine to use their models. You just have to ask first. This is what kcid did a lot in the past when he found models made by Racer community members, or others - just ask them. There were times when he couldn't get ahold of them, but they put the source for their models on racer-xtreme.com, and there was no license agreement, so we assume they're fair game...of course if any of those original authors object to our use we would remove it from the game immediately.