Hi!
Sure, I'll have a look maybe tomorrow. What's the best way for him to contribute? I suppose that we can't work with github, I think we could maybe ask him to submit a patch over gerrit? Or maybe I can just apply his patch but he'll lose ownership :/
You can cherry-pick patch from github branch and commit it to gerrit. E.g. see this as an example: https://github.com/wikimedia/wikidata-query-rdf/commit/eb9f6f37cfc2cc9ea2da0...
With git, author and committer do not have to be the same and while gerrit seems to limit committers on some repos, authors are fine.