You cannot embed touchdesigner in a game engine (at last with ease). VVVV does not comes with abstraction over DOPs SOPs etc, but both are still very limited regarding what datatypes they can process.
Are you asking about Luna? :) Sure! Luna comes currently with its VM but we are also working on a backend allowing to compile it to machine code, so every graph you write can be also used as a library and called for example from C.