Sorry I did not myself clearer. When I said legally, I meant to include by having users to pay something of course. There are multiple services (google play music, spotify, youtube music etc...) that for a monthly fee you have millions of copyright songs. A deal like this could be made. Or having a deal with record companies to let users pay for songs that then the users themselves create and share maps. I said it wouldn't be easier, but it can definetly be done. I know that implementing it referring to code wouldn't be a huge deal (the biggest part would be adapting it to the different plattforms). I don't know how hard it would be to aquire the required contracts to legally have a big library. But, again it can definetly be made.