It seems possible that Brave are building Brave Pro, which looks like its a subscription based service of some kind. A note on the Android implementation of the project reads (GitHub link):
"Implement the required runtime changes (profile settings, chrome flags, group policies, etc.) with the appropriate values that enable the Brave Pro experience. Using Brave in this mode with its default settings and making changes to the Brave Pro defaults require an active paid subscription.
When the browser has no active credentials for Brave Pro, the panel UI will promote the service and include the initial payment CTA. When credentials are present the panel UI will include the appropriate toggles for making changes to the default settings."
It also links to a private Google Doc.
“This website and the browser privacy tests are an independent project by me, Arthur Edelstein. I have developed this project on my own time and on my own initiative. Several months after first publishing the website, I became an employee of Brave, where I contribute to Brave’s browser privacy engineering efforts.”
It is ~95% open source. The remaining 5% of closed source changes are to the web-based UI.
Does that change the fact that Vivaldi is not a good privacy browser? Its content blocker is weak, its based on chromium which is affected by MV3, it can’t protect screen dimension fingerprinting, or canvas fingerprinting, or containerize cookies, or block 3rd party scrips and frames, or standardize specific settings like Firefoxes RFP, etc. Not a good privacy browser. Use a fully open source browser.