From what I understand, you need the original game to run it with OpenRA. Unfortunately I don't own Dune 2000.
oof, well that's a bummer. are you sure that the original game is needed to play a "dune 2000" mode on OpenRA? ⛱
I read claims otherwise, but I haven't tried.
also I looked for dune on GOG and found that there's only a wishlist. sighs.
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also some comments from there:
Baron_Chronus
well its funny how they're fine with a new movie being mad but not the games or any re-releases
MartyD82
That's a drag. About the licensing problems. I'd love to see the Dune 2000 Gruntmods Edition put in GOG and, thus, made perfectly legal.
Kingmen
All the rights apparently had reverted to Frank Herbert’s family, and when GOG contacted them they just said no.
A bit sad that no one will know the reason why the family isn't giving the rights to make a game or at least republish the original on GOG. 🥲
Also all I find on the internet about Dune 2000 and the like are arguments whether it's "abandonware", "freeware", legal, not legal, copyright, etc.
There are website's out there too claiming to have it as "abandonware".