Original thread: https://forum.megaglest.org/index.php?topic=5985.0
If you never played them here is a video:
Supposedly a WIP but pretty functional and almost 10 years later the original download link still works
No traces of license to be found and author is not active since 2018 however:
"Quote from: wciow on 7 September 2011, 10:01:51
Hmm, its been a while since I made the Undead mod. From what I can remember it is all made by me with just a few photos from burningwell which are Public Domain.
I like to release all of my works as Public Domain. Some mods such as Dwarves contain parts of magitech (mainly sounds) and the last "official" release by Archmage was marked with some CC license, which I don't mind.
I recently looked into helping the Planeshift RPG project and then recoiled in horror when i saw their licensing terms. Basically I get bored by licensing stuff so anything released by me will usually be Public Domain unless it contains someone else work which requires a certain license."
So they are under PD.