are others using imago?
I don't think we're likely to use this for Open States' new API, in large part b/c this is based on https://github.com/dobarkod/django-restless which hasn't seen an update in ~2 years. (we went down this road w/ django-piston, leading to a fair amount of regret)
Probably about equally feature-complete I have https://github.com/openstates/ocd-jsonapi/ which is based on django-rest-framework (a well supported & maintained library) and which is compatible with the http://jsonapi.org/ spec. I'm not sure if we'll go that route either but I figured I'd mention it as an option.
(I'm also somewhat interested in exploring something GraphQL inspired for Open States API v2, if that is of interest to anyone else)