JEdit: 4.3.2
The tip of the day says:
If you are used to Unix text editors where a middle-mouse button click inserts the most recently selected text, enable quick copy in the Text Area pane of the Utilities>Global Options dialog box.
But the option has moved to the Mouse pane in the Utilities>Global Options dialog box.
looks like kpouer already fixed it in jedit 4.4 and later.