Stemming is something that's needed in tagging systems. I use delicious, and I don't have time to manage and prune my tags. I'm a bit more careful with my blog, but it isn't perfect. I write software for embedded systems that would be much more functional (helpful to the user) if they included stemming.

For instance:  

Parse  

Parser  

Parsing 

Should all mean the same thing to whatever system I'm putting them into.

Ideally there's a BSD licensed stemmer somewhere, but if not, where do I look to learn the common algorithms and techniques for this?

Aside from BSD stemmers, what other open source licensed stemmers are out there?

-Adam