I guess you can call it stealing if you want. The word steal has many figurative meanings, such as ‘you stole my heart’. When a product fails, yes it eventually becomes impossible to use, even when you paid for it. To me it seems like misleading and hyperbole to call it stealing because you’re implicitly assigning malice to the business that simply failed, because they failed and aren’t getting value from the software becoming EOL, because they’re offering refunds to people who paid recently and haven’t had time to get value.
Do you call all products and business that fail or go out of business “stealing”?
If you read the letter and FAQ in their entirety, you will see they are not making it impossible to continue to use Finale. Customers who paid can continue to use it, for as long as their computer works. They are turning off new activations on new machines, in a year from now. It’s hard to imagine that mattering very much in the face of the facts that Finale is now dead, cannot be purchased, and is going to be obsolete eventually due to incompatible OS changes no matter what. But if you depend on Finale enough to not upgrade your computer, you can continue to use Finale as long as you want.