The bigger problem is that the lyrics are probably in direct violation of copyright unless they were used with permission. They shouldn't be part of the GPL cod

The bigger problem is that the lyrics are probably in direct violation of copyright unless they were used with permission. They shouldn't be part of the GPL code unless the copyright holder has permitted that too. As it stands there semm to be two readings from this: 1) the plugin is not part of the GPL code and de-facto unlicensed ("All rights reserved"), meaning the plugin can not be included in GPL redistributions of Wordpress; or 2) the plugin is part of the code and the code is therefore not eligible to be distributed under the GPL in the first place.