So having read through this thread and others, there is clearly some misunderstanding over Tremulous's status as an open source project and the associated legalities and legal concepts. I'm going to attempt to clear things up. These views are literally my own and specifically are not necessarily held by other people involved with Tremulous (though I hope they are).
Trademark
A trademark is a way of owning a particular sign or word that relates to your product. Tremulous is not trademarked and we have no intention of having it trademarked. It has been argued that common law trademark applies to the name in some territories. This may or may not be the case. I don't particularly care either way; it's a dictionary word and claming trademark ownership over it is pretty silly. I don't particularly care if someone calls something Tremulous or not; the name is not important.
Patents
A patent is a way of owning a particular invention or concept. In the case of Tremulous, the patentable concept would be something along the lines of "a video game containing aliens and humans that each build bases". My personal opinion is that the idea that you can essentially "own" a thought like this is absurd. The original intention of a patent was to protect a new idea so that it can be developed and brought to market while more resourceful competitors are prevented from "stealing" the idea. In this way the competitors would have to find other ways to get the same result so in theory innovation is encouraged. In practice what actually happens is large companies have big pools of patents that they trade between one another. Many, if not most of these patents are never actually developed and simply used as legal bargaining chips. In other words, the patent system is directly hurting innovation and development. There are exceptions to any rule. In particular the pharmaceuticals industry has a decent claim to requiring patents. They can spend inordinate sums of money developing a drug which can eventually be drawn on the back of an envelope. If patents for such inventions weren't in place it would be very easy for rival companies to immediately profit without any R&D on their part.
Tremulous is not patented, nor is there any intention of having it patented. I hope any attempt to patent the aliens versus humans concept would fail -- it's a ridiculous thing to claim.
Copyright
Copyright is where the author(s) of a tangible work are automatically given exclusive rights to it; i.e. they say who can do what with it. In Tremulous there are several things that are copyrighted: the code, the assets and the game itself. The fact that Tremulous is released under permissive licenses does not mean that it is not under copyright. The licenses rely on copyright law to work. Saying "you can't copyright something that is free/open source" is absurd. Virtually all software, open or closed, free or not, is copyrighted. I believe some people think that Tremulous is "public domain". Releasing as such means to give up all your rights to it. This is not the case.
The code is GPL. This means that anyone that distributes binaries of the code must also provide the source code. This restriction in apparent freedom actually promotes freedom. The GPL permits you to charge a distribution fee; though in the era of the internet this very rarely happens. There are no plans to ever charge in this way.
The assets are CC-BY-SA. This means that you are free to use them providing you attribute the work to the original author(s) and that you also share your changes with others in the same way. In many ways it is the asset equivalent of the GPL.
The game itself is copyrighted. By this I mean a game containing specifically a Dretch, specifically a Granger, specifically a Battlesuit etc., that when combined form the "Tremulous universe". In other words, the specific Tremulous game design is under copyright. The genre of an aliens vs humans with bases shooter is not and cannot be copyrighted (but potentially could be patented; see above).
There have been many contributors to Tremulous so there are at least dozens or possibly even hundreds of copyright holders involved. I am one (albeit probably the most significant). If somebody wants to do something with the code, the assets or the game design that doesn't fall under the above guidelines, each and every copyright holder must agree. In other words, even if I wanted to make a commercial version of Tremulous I couldn't, because I would need to get the agreement of said copyright holders and these are just too many of them to make this practicable.
It's kind of disappointing to read some of reactions to this whole debacle, particularly as the most vitriolic claim to have been playing Tremulous for a long time. Tremulous is not something I personally get a great deal of benefit from on the social aspect, I mainly did it because I like tinkering with games and software. Having said that it would be nice to feel appreciated once in a while or rather not be hated. If you're here at all it's because at some point you had fun with something that I made in spare time and gave you for free.