The low # of commits and vague name might be a bad signs, but check the repo description: Developed at Media Molecule and used internally for a title they've shipped, with feedback from domain experts like Casey Muratori. Those two points alone make me pretty excited to try this out.
And a brief explanation of why this matters: IMGUI frameworks are increasingly popular for editors, debugging tools, etc. because they eliminate the need for state synchronization between your 'engine' and the visualization/editing UI. You also avoid the need to duplicate your layout in multiple places - you have one function that is the complete description of your UI. This reduces memory usage and can actually be more performant in many cases because you can easily ensure that you're only ever running code to update visible UI. Things like virtualized infinite scrolling become quite trivial.
Among other places, IMGUI techniques are used aggressively in Unity's editor.