Which library implementation to use/work on?

Hi there,

I'm investigating GCJ for a project of mine to open up a Java library
to the world of [Objective] C++ via the quite lovely CNI interface.

My project depends on the Google protocol buffers library. Attempting
to compile this jar reveals that there is a slight gap in
java.util.regex in GNU Classpath.

I'm trying to figure out what I should do with my time:

1) Write a patch to classpath - problem, project appears to be dead?
2) Try and somehow compile against Apache Harmony - problem, project
also appears to be dead?
3) Change the protobufs library so it avoids the stubs in Classpath

It seems that trying to support GCJ will keep my project at the level
of Java 1.5 (or 1.4?) forever, as it's no longer being developed,
which is a shame.

I recall that some time ago Sun open sourced Java, but I don't know if
it's compatible with what I want to do or how it plays together with
GCJ (if at all).

Any tips for what I should do?

thanks
-mike