Rova 4D software?

Does anyone know if there is an open source (preferably) software to "paint" stl files like what ORD solutions is doing with their ROVA 4D printer? That looks like an ideal solution to multi-extrusion prints. Curious now that I got my dual extruder setup to work

---

Printers: Heavily redesigned TwoUp with E3D V6 and Robo3D R1+ with Chimera/Cyclops