This isn't ready for mass usage. Simply put this will replace the original kernel and allow users to use it just like they do with the current ReiNX or Atmosphere packages. Just stating that progress is being made and it's very close to being ready to release (that could still mean months away though).
zero instructions on installation. Nonexistent documentation.
you mean Atmosphere?
Mesosphere isn't even mentioned on the GitHub readme, but it does appear to be a component of Atmosphere.