Well, technically, you've got the sources, but there's no way to compile the firmware out of that as of now.
What I found is when I connected to my drone's wifi on my phone, I had a webspace of sorts where I could check various things about the drone, also there's an option to manually upload a firmware and there's also an SDK tab on the top next to the others. I haven't had time to mess with it more, but I think it might be useful.
So after connecting to the drone's wifi, you have to go to 192.168.42.1 (at least this is the drone's WiFi's gateway address for me) and then you'll land on said page.
I would strongly suggest not to upload anything as a firmware for now until we have some more detailed information about the whole thing.
