Gallium3D is largely designed around modern graphics processors (particularly GPUs with shaders) and the fixed-function NVIDIA graphics hardware that came prior to this has largely suffered in Gallium3D. These old GPUs being referenced are from the NV0x, NV1x, and some NV2x series graphics processors. Rather than continuing to let this support rot for extremely old NVIDIA graphics hardware, a new Mesa driver has been constructed that provides support for these old graphics cards and implements texturing, transform and lighting, etc. Most importantly, however, is that this driver actually works right now.
In a new Git repository by Francisco Jerez is the Mesa code that soon will be merged to Mesa master. This code drops the NV04/NV10/NV20 Gallium3D pipe drivers and delivers on a DRI driver for classic Mesa. The reincarnation of the Nouveau classic Mesa driver was announced on the Nouveau mailing list. Already in response to this, it's been confirmed by a user that OpenArena, Tremulous, and other lightweight Linux games are running fine while there are a couple games currently running into problems.
This is good news for those with these very old NVIDIA graphics cards, but most NVIDIA GPUs currently in use are well beyond the NV20 series. The NV20 is the GPU found within the NVIDIA GeForce 3 series, which was brought to the market about a decade ago. The Gallium3D driver will continue to be the sole focus for the GeForce 4 series and later.