Interesting. The main site says:
After careful deliberation, we've decided to make HellChess free for the masses !
Yes ! You read correctly !
So the windows users get the full version too, next to the GameBoy Advance users !
Get it from the downloads section
NOTE: downloads are disabled for now
The only two downloads available at the moment appear to be the demos (now obsolete?) for Linux and Windows. Oh well. I don't play chess anyhow- I was just curious about the title.