For Symbian OS based devices by Nokia (currently 9200 series communicators and the 7650 Series 60 imaging phones), one can develop applications in Java MIDP or C++.
OPL (Organizer Programming Language) is not supported but Symbian has a public OPL compiler & runtime that could work with 9200 communicator on their Developer Web pages. Though I vaguely recall that on that page it says that Symbian does not support OPL tools anymore either, they are available only to see how popular they still are...