Open source software can be sold for money. For example redhat selling cds with rhel on them, for quite a big sticker price. Free if you build it yourself but you have to pay to get a ready to use version.
or figure out how to build it yourself from source. But you can count on the lazy tax - esp. for windows (as building from source on linux is likely to be much more convenient).
"""
Brave Origin is:
1/ new, optional, separate build (stripped down, no telemetry/rewards/wallet/vpn/ai);
2/ free on Linux, one time buy elsewhere.
"""
So the stripped down version (at least the non-Linux one) will not be open source?