The license covers the code, not the trademark. You can use the code/software as long as you observe the license, you can use the trademark as long as you follow the rules set out by the trademark owner. E.g. you can totally use the code to make your own audio editor and distribute it, but the trademark terms might not allow you to call it "Audacity".
Copyright law and trademark law are different topics and have different ruling. Most software licenses (except 4 clause BSD or PHP License and few others) don't make any claims about names.
One might try to argue that a name used in software code and distributed under some open source license also gives rights to the name by being source ... but to my knowledge there are no court decisions.
Trademarks are actually still useful for open-source software, since they ensure that a malicious or incompetent party can't ruin the name of your software by shipping a modification that does bad things.
Jason Rohrer ran into this very issue when other developers made their own client for his game, using a variation on the game's name. They didn't respond to him asking that they don't use the name, and eventually he was convinced that trademarking the name is the right tool to project it. The original game client is still open-source (and maybe the server too, dunno).
GPL isn't "do whatever you want". It's "do whatever you want, as long as you let future users do whatever they want". That's what makes it such a good licence for the community.
