They’re open. Glowforge released the firmware well over a year ago. Might be closer to two. (So long ago I’ve forgotten when it actually was released.) 
But in any case, you can find the link to it in the Latest Improvements announcements that they post on the Dashboard periodically. That’s where it was first announced.
And a group of people have been tinkering with it since then. (No telling what they are making it do by now… It’s called Openglow.)