I’m working in an Apache Nutch project that involves some new plug-ins and customization in existing parts parts of Nutch, however, after reading Nutch’s code base and learning about its plug-in architecture, I believe someone could use part of Jenkins API to enhance the plug-in API in Nutch.
Nutch uses a similar concept, with the same name as in Jenkins, Extension Points. However, it’s quite hard to create a plug-in project separate from the core project (it uses Ivy and plug-ibs have some dependencies to the core project). And you have to extend certain classes and configure XML files to prepare your plug-in.
Part of this could be automatically done with inheritance + Java annotations. I’ll have a cycle for Open Source in the next days, and will give it a try to see if that really makes sense.