The Flow application (/server) is written in Racket and is made available under a GPL v3 license.
Our tools emit occam-pi, a parallel programming languages developed in the mid-1980s. (http://occam-pi.org) The compiled occam bytecode is interpreted by the Transterpreter Virtual Machine (TVM). (http://transterpreter.org/) More can be learned about both of these technologies at http://concurrency.cc. The TVM is made avialable under an LGPL license, and occam-pi (and the associated toolchain) is made available under the GPL... I think.
The interface for Flow (/interface) is made avaialable under an MIT license. (http://neyric.github.com/wireit/). I think.
The Flow icon is made avaialble by Lady Ada (adafruit) on Flickr under a CC BY-NC-SA license. I do not believe we have run afoul of that license by using it as an icon. (http://www.flickr.com/photos/adafruit/6856963336/in/set-72157629634862313)
The PLT group produces Racket, a dialect of Scheme. Its libraries are distributed as part of this application. (http://racket-lang.org/) Racket is made avaialble under the LGPL.
I do not know if I have inadvertantly forgotten a license in documenting this project.