I've looked at adding support for 3D Connexion's SpaceMouse and other similar technology.
Unfortunately, although they make API's, drivers, and documentation available for adding support to commercial software, they do not support open source software in a way that would let me distribute a copy of OpenVSP that included support for their products.
A new version of FLTK (our GUI widget software) is due out soon. It will include improved gesture support, so we should soon support pinch to zoom, two-finger rotate, three-finger pan, etc.
Rob