In addition to what everyone else said, registering your copyright in the US gives you the option of recovering statutory damages instead of actual damages from

In addition to what everyone else said, registering your copyright in the US gives you the option of recovering statutory damages instead of actual damages from an infringer, which is real useful if, say, the work is FOSS and you'll have trouble demonstrating you lost more than $0 profit because of the infringement. https://en.wikipedia.org/wiki/Statutory_damages_for_copyright_infringement https://en.wikipedia.org/wiki/Statutory_damages_for_copyrigh...