It's not clear how far along it is, but progress is progress and gives Epic themselves a massive head-start.
Probably not even close to being production ready, but this is fantastic news and will hopefully prove to Epic how good an idea it was to give subscribers code access!
This is what happens when code is open guys, people can help. While it's not FOSS it's better that it's open to subscribers than not open at all. Power to the community!
I cannot wait to see what else happens and how long it takes for the Linux editor to become stable.