If they think they can make a better file manager, great, go ahead. But including transports in the file manager means that remote data only looks integrated, it isn't actually available to local apps.
Or (just as bad) they'll decide they need a copy-to-local and copy-back-to-network mechanism, which will work for some files opened by some apps but not all. Arghh.
Nemo (under Linux) does that for some protocols (eg. Android media transfer), and it is very annoying, especially as there are already FUSE drivers for (at least some) such protocols. In practice it means that the only thing you can do using Nemo is copy/move files around.
That's a very good point, I didn't even think about the aspect that FUSE is available system-wide, for all other applications to use transparently. That makes Spacedrive seem to come up really short, in comparison.
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.
Yeah, FUSE is Linux only. But for completeness, for macs there is macFUSE, and for Windows there is winfsp. Both of these have fewer filesystems than FUSE, and I've used neither so I don't know how well they work.
https://github.com/libfuse/libfuse
https://github.com/libfuse/libfuse/wiki/Filesystems