It is open source, but had some controversy. Most prominently the addition of telemetry a few years ago, which was never included in the builds managed by Debian or most other distro maintainers. They also added a Contributor License Agreement which lets the Audacity project change its own license (even to a non-foss one, though they promise they won't) without needing to have the change approved by any individual developers.
I'm not completely sure but I think they removed it at some point after the public backlash (which was 3 years ago now). For the Windows version at least, there apparently used to be an option during the installation wizard for setting whether telemetry is enabled or not. Most Linux distros never had the telemetry at all. I don't know about Mac.