This is not a subscription to use the browser. You can always build it from source and use for free, as designed.

This is a commitment to support the development, because the development should be oingoing. Not Netflix-style, but Patreon-style.

(Also see how JetBrains handles "subscriptions" to their closed-source software. Once you've paid, the version is forever yours. Updates are bought with some additional sums if desired.)