prior to CS4 a simple text file was all that was needed to create your own FileInfo panels but starting with CS4 these panels are Flash applications. Adobe has released an SDK that supports the creation of new FileInfo panels.
there are three major pieces to this component
each can be used without the other but together they implement a complete creative commons XMP license metadata package.
download the full package in .zip format. make sure to save the file on your hard drive where you can easily find it later then follow the follow the instructions in the photoshop tools blog post to install each component in it's proper location. if you use the creative commons XMP templates there is some personalization required.