As I mentioned, it is a research project, so I would not expect production ready code or multi-browser support. They are indeed not supporting the old version, as they are rewriting almost everything from scratch.
Last time I had contact with them, they were exploring using Plasmo [1] as building block for the extension, instead of doing everything vanilla as they did in the 1st version, which would offer cross-browser support out of the box.
But meanwhile, you can check the code [2] and add the FF manifest yourself to try it out.
Also [The old version of SenseMap is no longer being maintained. A new version called HistoryMap is currently under development ] > site is dead .