All of the other options return {error, "Not implemented"}. It'd be nice to finish off that part of the API, but short of that, the incomplete implementation should be noted in the docs (Known Limitations?) IMO.
I committed a version that supports all socket options. The original driver code was implemented prior to getsockopt() API call being available in 0MQ, hence the missing logic.
All of the other options return {error, "Not implemented"}. It'd be nice to finish off that part of the API, but short of that, the incomplete implementation should be noted in the docs (Known Limitations?) IMO.