I'm not sure why SE is going so crazy about the copyright stuff. There is tons of precedent in the game industry for players using in-game musical instruments to cover their favorite tracks in other MMORPGs such as Lord of the Rings Online and Guild Wars 2 for instance. So either it is some weird Japanese Copyright Law or their Legal department is just overly insecure about being sued. Either way - the Legal guys need to understand they have licensed us a piece of software or a tool - and therefore they cannot be sued if a user decides to use the tool to commit copyright infringement. If that was case Adobe would stop selling software. You don't sue Adobe when an individual profits off of copyright infringement when they produced their content with Photoshop for example.