chess4j is a Java based chess program. The goal of chess4j (besides just having fun) is to serve as a test bed for various interests, including parallel and distributed computing, machine learning, and exploring different JVM languages and technologies. (Note I’ve done very little in any of those areas yet!)
chess4j is distributed under the MIT license. See LICENSE.TXT in the download for details, but essentially it means you can do pretty much anything you want with chess4j as long as (1) you don’t hold me liable, and (2) you provide attribution back to me.
You can also download the source code at https://github.com/jswaff/chess4j.