So I got it to work on Galileo and it apparently can work in newer Eclipse versions.
Just download the zip file, go to:
- Help->Install New Software
- Add-> Archive and select the zip file.
- DESELECT “Group Items By category” option at the bottom.
- install.
There are more details here (search for comment by ‘stokiematt’ towards the bottom). http://sourceforge.net/projects/eclipsejsonedit/forums/forum/957258/topic/3311846