This is a similar project but fully open source (and probably less mature). The lead dev is very active and responsive. https://immich.app/
https://github.com/photoprism/photoprism/blob/develop/LICENS...
Selling open source or free software is fine.
As such you could fork it, tweak the code around the license verification to always return TRUE or whatever, and you would be running a "pro version" of the software.
The developer simply trusts that people who like the software will purchase a license, or the fact that the majority of people out there are not programmers and would not be able to rebuild the software for themselves. Besides, the product is also offered as a SaaS.
would be cool if also had dynamic shared albums as google photos has with facial recognition