Contributions are always welcome! The tracking JIRA is [HRCPP-19] Remote Queries - JBoss Issue Tracker, it's assigned to nadirx but I doubt he's working on that right now - still, please check with him before reassigning.
The query language is not ANSI SQL but JPQL. If you want to implement querying, please use Java client and server (with some parts in Scala) as a reference implementation.
I have unassigned it. Come and talk to us on IRC on Freenode #ispn-cpp-client