Take a look at the very excellent work done by the Open3DP group at the Univ. of Washington. They've done a lot of research into both FDM type systems (Makerbot, Prusa Mendel) as well as powder based systems (ZCorp).
The ZCorp formulas have been pretty exhaustively reverse engineered. The necessary components to build an open sourced ZCorp-like printer already exists - the ink shield, motor drivers, etc. All you need is the guts to do it without getting sued by ZCorp's army of lawyers. I've heard in the UK you are allowed to build something for personal use without worrying about violating patents. Here in the US that is illegal, even if it's for personal use.