Are you adding Gratipay to your own GNU FM site, or do you want to see it on Libre.fm?
The same info in that webpage is in gnufm_install.txt in the root of the repo. I don't see how adding a static page would be a violation. In our case, we do use PHP to load a couple of libraries but the content is 100% static. If you did this, I wouldn't consider it a violation. But I'm no lawyer.
