They have somehow managed to write a 500-word article on their project, advertising that it's "built native", without mentioning which platforms it runs on.
The answer appears to be "only macOS, maybe Windows later".
We planned to release a Windows version in Jan 2018. Unfortunately, we got trouble with Swift compiler on Windows (not officially supported, only Linux and Unix). We decided not to wait for Swift and rebuild all the whole thing in C/C#. That takes longer so we hope to release it soon
Because Linux has too many distros. We didn't decide to use Gnome or C/C++ to build the interface. Since the team is very small, we have to focus on our best.
The answer appears to be "only macOS, maybe Windows later".