I have a copy of LuxRender that I got when I just started with Terragen2. I also discovered blender at that time.
The copy of Lux I have was free at the time. I don't know if its a full version or not. May have just been free for the initial OSX release? No idea though.
I have never used it, don't know how to use it, and don't even really know what the hell it is. So I don't even know why I still have it.
I went on a downloading binge when I found out about how 3D had really gotten to a place that I could learn it at home. Even bought a ton of stuff from NWDA when I bought TG that I still have not used (I knew/know that I will use it though! And really glad I did buy that stuff now that NDWA has taken a very long sabbatical!)
Anyway, I use mental ray and TG2-3 only, right now. 3rd party stand alone renderers seem to me to be only for people above my experience level.
I do have my eye on Arnold renderer though!Been watching what they are doing for a while now.