I would imagine that is the plan in some way. From their legal FAQ: "Through GitHub you can access UE4 C++ source code from Epic and also see code contribution

I would imagine that is the plan in some way. From their legal FAQ: "Through GitHub you can access UE4 C++ source code from Epic and also see code contributions from other developers across the community. We have lots in store for this channel, and we're looking for feedback on what you'd like to see here as well."