“The company has renamed its Free plan to "Personal" and now requires that businesses with 250 or more employees, or higher than $10m in annual revenue, must use a paid subscription if they require Docker Desktop.”
Docker made itself the default on every developer laptop and then sent the bill. The engine stays free and open source. The desktop app most Mac and Windows users actually run does not. Docker sold off its enterprise business in 2019, and the licence change is the business model it has left.