They list MoveOn as a key partner:
This document clearly states the organisation is founded by Berine Sanders supporters:
And they built something called the "Resistance Calendar", containing events like:
I mean for the most part it seems to be stuff I would support (personally), but to call it party neutral is at best true by way of technicality.
I doubt you find many Republican events on that calendar. Of course, I wouldn't expect to given the name of the group, but let's not play games and pretend it isn't partisan?
So it'll make an application that supports primarily republican causes too.