fwiw Jafar announced last week it would be open sourced in the next couple of weeks [1], and a number of people have access already and are helping with documentation and the like.

Falcor and Relay are conceptually similar but Relay is much more of a query engine, and Falcor isn't so much.

[1] https://plus.google.com/events/ca3l6qalpu0uqcce58a379006m0