Phoronix: Come Play This New Linux-Native Game With Us!
S2 Games may not be as well known as id Software or Epic Games, but what distinguishes them from most of the other game companies is that they actually support Linux. With S2 Games' Savage 2, for example they provide a Linux-native game client...
The NDA allows you to talk about the game, but not to post media.
Heroes of Newerth is based on the concept of DotA, but enhances it, has nicer graphics, more community features and is standalone. In the closed beta, they focus on the game in general, on the engine and the ports to Linux and Mac, while more new content not found within DotA will be added until release.
If you want to know more about DotA, read THIS article on Wikipedia. And again, it is only based on that concept, so ignore the screenshots from that article. The game looks *much* better.