The following is a note gleaned from the mailing list of someone describing how to get Java working in Conkeror under OS X. It could use a rewrite to be more intelligible to newbies.
downloaded java embedding plugin http://javaplugin.sourceforge.net/ placed the 2 'files' in the binaries directory in the zipped files (JavaEmbeddingPlugin.bundle and MRJPlugin.plugin) in /Library/Internet Plug-Ins/ and now java works in conkeror for mac os x.