Well I’m 100% sure it’s not software emulation because my machine is slow (1.6ghz, 1gb ram, 256mb nvidia graphics card) and my engine runs fine, dynamic shadows - per-texel lighting (normal maps/specular maps), etc. with reasonably a high poly count.
If that was software emulated it wouldn’t run at all!! 
As I understand it, mesa3d started as a software implementation but then got full hardware support? You can turn on software mode, though. On their website, they say :
“Ongoing: Mesa is used as the core of many hardware OpenGL drivers for the XFree86 and X.org X servers within the DRI project. I continue to enhance Mesa with new extensions and features.”
and…
“A variety of device drivers allows Mesa to be used in many different environments ranging from software emulation to complete hardware acceleration for modern GPUs.”
It also says that it has hardware support on the wikipedia page too:
http://en.wikipedia.org/wiki/Mesa3d
I just checked the includes (/usr/include/GL/gl.h) and the very first thing in it is:
/*
- Mesa 3-D graphics library
- Version: 7.6
Also, if you check the dependencies of SDL, mesa3d is the one and only reference to opengl in there. AND (sorry for going on-and-on here) if you look at blender’s site, they say that many people get better performance from mesa than from the propriety drivers!
I would like to run glewinfo for you but I need to update my repositories to do that, but I can’t because I in a stupid country with crap internet. ( I’ve used up my month 2GB data-cap 
)
Maybe mesa has become something else since 10 years ago when those demos were released? And the newer stuff that you said that run at 1fps on nvidia hardware - as I understand it nvidia was not being helpful on the open source front and so there hardware didn’t have support in mesa, but recently they released closed source drivers that could interface with mesa/linux just recently (about a year ago?).
…or something like that, but I could have my wires crossed somewhere!
