Hi,
I am working on an AI related application. For this application I need to have a rule engine. Jess is a good rule engine completely written in Java. But for my application I can’t use it due to license restrictions.
Can somebody tell me an open source rule engine written in Java?
Drools is a prominent open-source Java rules engine, and it uses ASL2 licensing. I haven't used it personally, but some colleagues of mine have used it successfully on a few different projects.
An open source off the shelf rules engine might be complete overkill for your application, I've used Drools before and it's pretty heavyweight, you'll also need to understand the framework before you use it - with Drools it's not too bad, but it might be more appropriate to write your own DSL rules engine in something like Scala/Groovy/JRuby.
There's an interesting article here that talks about building a Groovy based rules engine:
http://www.pleus.net/articles/grules/grules.pdf
Work out what suits you best from these options and go from there.
Drools is by far the most feature loaded and extensible, it has a lot of production implementations too. It is ASL2 as said in the previous post.