Isn't this a problem that the market will correct? If Arc the language has a significant enough following, then "Arc" in common use will refer to the language. I'm not saying people should go around picking names others have used, but it seems a little heavy-handed to assume that because a few thousand people have an attachment to a name it is now off limits for everyone else. Moreover, at what point does it become ok? There's also Ark the YC company: http://ark.com/ is that fine because it uses a k?

Taking a look at it from a different angle, even in the case of the legal framework for names - trademark - having Arc the language and Arc the VM thing would be fine.

The truth is, if you don't want people to collide with your name, picking a 3 letter common word probably isn't the way to do it.