Phosphorus and Lime

I'm in the (free open source) market for a spam filter for PHP -- and here's the catch -- not tailored to Word Press. There is not any pressing need at this time for it -- but I anticipate needing it shortly for a couple projects I'm working on.

I've found a couple scripts that look promising:

Bad Behavior
- download
- installation guide

I've only had a chance to browse the code, but from the write-up this sounds like just what I'm looking for and easily ported

Spam Karma
- download
- wiki

This is tailored to Word Press but looks like it could be portable

At a glance, it appears as though they take slightly different tacts with BB comparing header requests against a blacklist of bad agents and SK2 comparing submitted content against a blacklist of terms. But I'd have to look more closely at the code to really understand their respective logics.