As far as I understood it: GnuPG started to implement stuff from the standard before it was finished, the standard continued to improve and GnuPG refused to change code already written.
Using new technology in something small and unimportant like a setup script is a perfect way to experiment and learn. It would be irresponsible to build something important as the first thing you do in a new language.
There is nothing in the open source licensees that prevents charging money, in fact, non-commercial clauses are seen as incompatible with the Debian Free Software Guidelines.
And there is a lot of companies out there that make their money based on open source software, red hat is maybe the biggest and most well known.