Because who decides what projects deserve how much? Who decides that a project is even worthy to receive anything at all? If there was such a government program, what would prevent masses of inexperienced developers to start pointless projects, open source them, and file a claim to receive money from the government?
In order to take advantage of this compulsory license, a notice must be sent to the copyright owner along with a fee set by the U.S. Copyright Office, known as the statutory fee or statutory rate. The fee for recordings is currently (as of 2017) 9.1 cents per song (or 1.75 cents per minute of playing time). To verify the current rate, check the Copyright Office's guide to compulsory licenses. On the site, you can click “Mechanical Royalty Rate.”
Maybe we can try finding useful metrics then. And of course they could be gamed but then we can adapt and improve. By example start with number of stars on github or number of forks or even views (with verified users). Actually, we have such kind of measure, it's called advertising. It's one of the few working business models on the net but it works with a kind of bizarre tax on physical goods. Why not with a levy ? Edit: typos
