Still, I would like to point out that such a deep game cannot be judged by the assets they "stole" (they stole nothing, everything was asked for or free), but from a gameplay perspective.
Sorry, but no. From the mod description for one of the old releases (http://civilization4.filefront.com/file/Fall_from_Heaven_2;64936):
A huge thanks to the artists I shamelessly cut tiny pieces of art from to make all of the icons and graphics used in this mod. Justin Sweet, Brom, Don Maitz, Keith Parkinson, etc etc are all amazing and contributed (unknowingly) not only the amazing art, but inspiration for a fantasy world through their work. Several icons are used from the GuildWars game for their clear evocative style.
Some of the songs heard in this mod are from the Eclipse Mod for Half-life 2 and Arcanum. Additionally there are small cuts (5-30 seconds) of songs from Enya and Cirque du Soleil throughout the mod.
Justin Sweet: http://www.justinsweet.com/
Keith Parkinson: http://www.keithparkinson.com/main.php
Don Maitz: http://www.paravia.com/DonMaitz/Version2/index.html
Eclipse Mod: http://students.guildhall.smu.edu/~eclipse/downloads.html
Nothing was asked for, everything was taken without permission. Notice how he says all "unknowingly" contributed.
You absolutely *can* and *should* judge the professionalism of a mod by everything, not just gameplay. Ripping off other people's work without so much as asking them does not deserve any form of praise.
Edit: Randomly hit one of the sites he linked to:
http://www.bromart.com/contact.html has this gem:
Licensing of Brom's images - Yes, that's how he makes his living. If you would like to license some of Brom's work email us for details.
Certainly not "free", wouldn't you say? The current "credits" page has 3 "used with permission" listed, out of 13.