I made a tracker for delayed-source releases (BUSL and FSL licenses): https://captnemo.in/finally-foss/

Might add JSON feeds, RSS for now. Main goal was to validate if anyone is using these releases 2 years later (forks?), and the answer seems to be no. The FSL premise for delayed releases is primarily around risk mitigation (if company goes bankrupt or bought out), and that is also yet to be tested. Most FSL/BUSL forks are at the moment of license change (OpenTofu for eg).

As another datapoint, Oxide is maintaining their fork of Cockroach, but has ignored all future releases (that became FOSS).