This is correct as of last year, and probably this year, too, but I can't say that for sure. They could very well have made some good tweaks and upgrades to the hardware/software.

Last year, Thinkpad X200 laptops (using Libreboot and Trisquel) were used in the 3 session rooms. The cameras were by Elphel, also running free firmware. The laptops processed the video feed with some complicated gstreamer pipeline and sent the result off to the FSF's Icecast server. The stream could then be viewed in the video player of your choice (such as VLC) or directly in a web browser. A small JavaScript application on the LibrePlanet site let you quickly switch between the 3 rooms and used Icecast's XML API to retrieve some fun stats like how many people were currently watching the stream.

It would be nice if they could get beefier machines on site doing the a/v work which really taxes the X200 (the gstreamer processes get nice'd to give them higher priority and the fan is set to max via a kernel setting), but there simply aren't any better options for fully free computers right now that can be reasonably transported. Or maybe the FSF has found something that I don't know about. We'll see!