Hi I start this thread to improve the workings of this GPL mod and GPL engine on the open radeon driver.
On r300 it worked ok, be it slow.
Now I upgraded to an r600 powered chip (RV730), And it has texture issues, white terrain, half the units are white. The rest works more or less flawless, and the performance is very good.
It's most likely a s3tc issue.
Spring with Balanced Annihilation mod will not even start here (rs780, mesa from git) unless I disable shadows and advanced unit shading in ~/.springrc (bug 25024).
But apart from that it works with some graphical glitches (eg. ground texture is white as you mentioned).