[thallian]

I absolutely loved it, especially the vast array of maps. To once again defend Minas Tirith from the Nazis...

There is also ET: Legacy, an open source implementation of the game: https://www.etlegacy.com/

But I don't really know if it's any good.

Edit: looking at it I now realise that the game already was released as open source, the ET Legacy project is based on it and fixes bugs and stuff :)