As more and more content creators begin embedding license information into the metadata of media files the amount of benefit from displaying this information increases.
The open source audio/video media player Banshee has already implemented this functionality:
liblicense is a software tool developed by Creative Commons to reduce the implementation time for this functionality. It already includes the logic to read (and write) metadata information from a wide variety of file formats.
Also, if you want to see how this is implemented in Mono (what Banshee is written in) check out their source code or just view the src/Core/Banshee.Core/Banshee.Collection/LicenseInfo.cs file