Slic3r is an interesting project that goes in that direction. Only for printing though. You can feed it an STL exported from sketchup and it will generate a too

Slic3r is an interesting project that goes in that direction. Only for printing though. You can feed it an STL exported from sketchup and it will generate a toolpath. And of course it's all on github and completely free and opensource and multiplatform. The major problem with it is that sketchup is a mesh editor, not a solid editor, so it sometimes exports geometrically impossible (non-manifold) objects.