That was my reaction too, but FUSE is Linux only while this is cross-platform.

I am not convinced file managers need to be cross platform. There are plenty that will run on any desktop, IMO mobile platforms need different functionality and a very UI.

The real product as described on their website (not the github repo the linked) is that it is a drop box like sync service integrated into a file manager. I think most non-geeks will find it confusing compared to something that integrates with the familiar OS default file manager.