Phoronix: The Vega State Tracker Gets Cleaned, OpenVG 1.1
Chia-I Wu, the developer who previously worked on the EGL state tracker, brought Mesa to Android netbooks, and allowed Nouveau to work on Wayland (and now is doing work for LunarG), has some improvements to the Vega state tracker. Namely he has cleaned up this Gallium3D state tracker for Mesa and additionally has a branch containing OpenVG 1.1 support...
How they compare, maybe can be incorporated into mesa?
The base libShiva is not at all relevant. It's an abandoned, pure-software, scene-graph renderer vs a modern hardware-accelerated Gallium renderer based on an open and standardized API. ShivaVG is more interesting (although wrapping OpenGL vs calling to Gallium3D directly is not ideal), but I can't for the life of me find a source download link for ShivaVG, just that one article you linked talking about it. Maybe I'm just blind and you can find a download or even a repository link for ShivaVG.
Yes this one. I have been testing this half year ago with some demos (animations), and it was very fast and smooth on my radeon M22 (Mobility X300). Of course having such functionality in gallium directly should even inprove performace, but last i tested OpenVG/vega in gallium, it wasn't very good. (btw. but actually there are also no animated demos in mesa for OpenVG).