To use Groovy from inside jEdit download this
. You'll need a fairly recent jEdit distribution.
Right now BSF isn't yet released with inbuilt Groovy support so you have to add the following code to the startup script in
<MODE NAME="groovy" FILE="groovy.xml"
The Groovy mode for jEdit is in the SVN since July, 9th 2004.
It is included in standard jEdit setup.
In order to know if you have this mode, check that the file <jEdit_Home>/modes/groovy.xml exists.