Gergely Papp

Definitely not the right place, I barely ever check this forum. FreeplaneGTD addon issues are to be reported on the issue tracker. https://github.com/gpapp/FreePlaneGTD/issues As the developer of the add-on I strongly suggest, to use a freeplane version, that is compatible with the addon. Such an old freeplane won't be able the add on that requires 1.5.0 or higher. Also there seems to be issues with the Openjdk shipping with Linux distributions, you should install oracle jdk if you encounter start-up...

I've started on a web-based mindmap project a while ago, see https://mindweb.itworks.hu It could be used as a back-end to freeplane. The latest development branch allows true collaborative editing with websockets based interfaces. Contact me if intereseted.

FreeplaneGTD 1.9.2 released to fix this issue.