From what I can see it is a set of common functions wrapped in an API you can use from your front end application. I don't know what all those functions are however email and auth appear to be two of them.
Also pretty confused as to what this does. There's a few examples and sample code for initialization, but I have no idea what the use cases are, what type of "backends" I could build with this, how it's better/different than popular existing frameworks, etc.
the main purpose of a backend is the access to data... e.g. like Firebase. For open-source approaches, ArangoDB Foxx looks more intersting with this regard: https://www.arangodb.com/foxx
I've looked at the Github page, read the README, and skimmed the documentation....
...and I still have _absolutely_ no idea what this does or what its intended purpose is. None whatsoever.