Earlier quoted context omitted.
>git is a good example. It's GPLv2 Is it a good example? I'm not very firm with licensing. As far as I understand it git is not a library or a programming language, which means that even if you use it commercially you're not really modifying or repackaging it in your software, so there's really no duties arising out of it even if you use it on your servers. Your software is just communicating with git. Please correct…
git is a both domain specific programming language and library of software routines that enable version control. Curious why you don't see it this way.
('DSL' can be a valuable lens to view a program though. Just like viewing things as eg file systems or databases can sometimes give you deeper insight.)