Will Farsight2 work with older versions of GStreamer than the ones mentionned in the README?
No, it won't.
When I run tests/gui/fs2-gui.py, I have a deadlock.
I run Debian and when I try to start a video session, the "codecs-ready" property never turns to TRUE?
Debian maintainers think they're smarter then the upstream maintainers and use their own copy of ffmpeg instead of the one provided by gst-ffmpeg. They forgot to disable ffenc_libtheora (which is broken). They know about this problem, but have yet to fix it. Solution: use a better distribution or remove the gstreamer0.10-ffmpeg package.
I run Gentoo and my application crashes when I enable video?
Avoid gst-plugins-farsight 0.10.5, use 0.10.4 or 0.10.6