This is a question that's come up a few times, and though I'm not sure I've ever come up with a clear answer, there's a few things to remember as far as copyright law is concerned;
- As the creator of a post, you obtain copyright of said text when you submit the message.
- Nothing on the site circumvents copyright law, or makes you give away rights to your copyright material. I've seen it written (but have not been able to confirm) that it is impossible for a site's T&C to make you give away your copyright carte blanche.
- As with email, just because people have access to your text does not give them permission to use it as they wish. Apparently it is illegal to repost emails in a public forum, so I'd assume the same applies for reposting forum posts outside of the original site.
That said, in posting on RPoL you have given us permission to store and display the post on this site, and similarly given the GM(s) permission to utilise that post within their game.
Character names are, for better or worse, not protected by copyright (though they can be trademarked, if you go to the bother). Putting aside what's the nice or ethical thing to do, it is legal for GMs to do whatever they want with your character names. The description etc that goes along with it is protected by copyright (that you hold the rights to).
So if you've posted your description to your character description then I think you've already given the RPoL and GM consent to store it there. If the description was only via PM and the GM has now posted it in your character description -- well that's a grey area that I have absolutely no idea about (on one hand you've posted it to their game, on the other it's (as far as I'm aware, at that stage) private correspondence). The nice thing to do in either situation, especially considering your character hasn't been integrated into the storyline, would be to remove all information immediately. In running games we do not expect GMs to suddenly wrench characters out of games in a manner that's jarring to the story, but (purely based on what you've described of it) this situation just sounds like character/idea hijacking.
The advice that BBR gave is the best one available (plus facemaker329's advise not to worry too much about it). I can't start making judgement calls on this kind of thing as I'm not a lawyer, and alas RPoL cannot afford to obtain the services of one.
We will absolutely strenuously enforce and rights (copyright or otherwise) that any and all member has, if we definitely know it for fact. Unfortunately it call gets a bit grey in collaborative storytelling.
This is all my opinion, so is most likely largely incorrect.