In the United States. Which despite being absurd as it is in so many ways, is the largest single market for Ardour (Germany is second, though alternates with the UK from time to time). The original/lead developer is also based in the USA, as is Harrison Consoles, the company that uses Ardour as the basis for its "more commercial" Mixbus product.
Note that I am a staunch advocate of ending software patents: I have testified in court 3 times regarding their stupidity, and donated a large sum of money in 2018 to the EFF to help fight software patents in the USA (money I recieved from appear in court :)