Just as an FYI, I managed to get the complete Lejos stack including the Eclipse plugin working under a "modern" Linux software stack including the following:
Oracle JDK 1.7.40, 64 bit version
Eclipse 4.3.1 Kepler
Lejos 3.0 (CVS version - modified)
Eclipse Plugin 1.2.0 (CVS version - also modified)
I had to fix (patch) several problems with the Eclipse plug-in, and the Lejos 3.0 software, but everything seems to work well now. If anyone is interested, I can make my patched version available for download. I haven't tested under Windows or OS X, but it's quite possible that these fixes would work for those platforms as well.