The JSR-198:A Standard Extension API for Integrated Development Environment expert group has made the early draft available for review.
I really love this JSR and I am very happy that is now making progress because I played around in the past with Oracle JDeveloper Plugin APIs and I was disappointed that my work could not be used in other IDE...
Oracle JDeveloper 10g (10.1.3) API will be based on the JSR 198. Take a look the Oracle JDeveloper Extension page.
On my side I have to dig out the old extensions that I wrote for 9.0.3 and migrate them to 10.1.3, I will start with the small Lejos extension, if I can find it... It has been so long since I did not play with my legos...