Light Table is open source by Chris Granger.
From the post:
Today Light Table is taking a huge step forward – every bit of its code is now on Github and along side of that, we’re releasing Light Table 0.6.0, which includes all the infrastructure to write and use plugins. If you haven’t been following the 0.5.* releases, this latest update also brings a tremendous amount of stability, performance, and clean up to the party. All of this together means that Light Table is now the open source developer tool platform that we’ve been working towards. Go download it and if you’re new give our tutorial a shot!
If you aren’t already familiar with Light Table, check out The IDE as a value, also by Chris Granger.
Just a mention in the notes, but start listening for “contextuality.” It comes up in functional approaches to graph algorithms.