The standalone has been released! You can find it on Steam here. Keep in mind that this is an early alpha, and is going to be buggy.
We're working on getting new data and maps available as quickly as we can. Like the game, once we have something available, it'll be a first pass, and not quite as polished as what we might want it to be. However, we feel it's more important to make something available as quickly as possible, rather than making it perfect first.
Update 1: An initial version of the map is available here! This is a very early version, but more is definitely coming soon.