Bunch of tutorials using the language: https://probcomp.github.io/Gen/tutorials.html
Paper: https://dl.acm.org/citation.cfm?id=3314221.3314642 (is this article paywalled? I'm on my university's network so I don't have a paywall)
The syntax doesn't seem to be changed compared to Julia (so is it actually a new language or just a library? Not sure, haven't seen Julia code in a while.)