In a way, you are buying commercial. The Ardour people are selling downloads of their binary builds for $1 per download (or more, if you choose), along with some access to support I think.

It's also possible to, for example, 'apt-get install ardour' and get a similar version in Debian Buster. I presume there are lots of other operating systems that this is built for, so Ardour does make a significant contribution to free software.