Given the distributed nature and growing number of people building on top of JuMP, I think it's time to have a developer-focused chat room:
I'd like to restrict the scope of discussions specifically to development questions related to the "JuMP stack", i.e., solver interfaces, MathProgBase, JuMP, and JuMP extensions (official or unofficial). Feature requests are out of scope unless you're willing to implement them yourself!
The theme of the channel is bringing the JuMP stack into a coherent state for a JuMP 1.0 release sometime in 2017. This specifically means tidying up and documenting JuMP internals among other things.