Widelands: an open source freeware remake of
Settlers II.
The Settlers II.5: Return to the Roots: an engine recreation (and improvement) of
Settlers II which requires the original data files.
Freedoom: A project to create a completely free data WAD for use with the Doom engine, resulting in a freeware
Doom lookalike.
Blasphemer: Just like Freedoom, but for
Heretic.
FreeLords: A
Warlords II remake/clone.
LordsAWar!: Another
Warlords II clone.