The source-code is probably based off OpenDUNE but I'm pretty sure the art isn't. They'll be taken down for the art for sure ...
Haters gonna hate.
Dune 2 was released as freeware if memory serves me right.
I know they still can send them C&D letter, but I don't think westwood/ea will bother.
Yep, looks like they just recreated the game engine. You still need a copy of the original Dune 2 data files to play the game.
As far as I can tell from their wiki, OpenDUNE was created by disassembling the original game and recoding the assembly in C. I wouldn't say the copyright issue is clear-cut, here.