This repository contains a few gnu tools compiled for quartz. Its based on the work of Sharpie, but with significant patches on inkscape to make it work for Mountain Lion.
The main tool here is inkscape, which will run natively (i.e. will not run inside X11 or XQuartz, but directly using GTK Quartz backend).
Just brew tap acornejo/quartz and then brew install <formula>.
To install inkscape do:
brew install inkscape-quartz
Expect the build to take about 20m.
You can also install via URL:
brew install https://raw.github.com/acornejo/homebrew-quartz/master/<formula>.rb
brew help, man brew, or the Homebrew wiki.