Java Rule Engines

I am looking for an open source rule engine, and so far what I see is that there was a lot of development of different rule engines (like Drools, JSR-94 etc) few years ago, but I don't see much action around this topic currently. All the articles that I found are dated back to 2004 - 2008. I tried to use Drools' tutorials from "codehaus", but when I click on "CSV" link to download source code for tutorial, I get "Page Not Found".

Does anyone has a positive experience with any of open source rule engines? Any articles to read about what is going on in this area?

Did you try googling for "Drools"?

Yes, I did (this is what I started with). When you Goggle "Drool", the top in the list is "Drool - JBoss community" link where you can get link to "Documentation". Over there there is a link to manual, but I don't see any link to beginners tutorials. The link that I found for tutorials, doesn't contain source code. This is what is not clear for me - if there is an active development of a tool, but there is not much recent activity around this tool in Java world, then the question is if people are still using this tool. That's why I am looking to hear about other developers experience with different rule engines.