> Plenty of software makers feel completely free to make incompatible upgrades That isn't really contradictory, is it? It just means that you can do that only

> Plenty of software makers feel completely free to make incompatible upgrades That isn't really contradictory, is it? It just means that you can do that only if you dare to break some of your consumers. Otherwise, you have to bear the costs of maintaining all those undocumented features. The law simply says that any observable behavior becomes an implicit promise.