Source Code Escrow
We've had years of OS lockdown at some organisations because somebody bought software years ago which is essential to the business. We can't upgrade the Windows version because it will break a business critical application. And the software supplier ceased trading eight years ago.
I've worked with a few perceptive IT managers. Prior to year 2000, one of them asked small companies for source code for their products; some handed over tapes and others signed escrow contracts -- source code resided in a safe place, to be accessed and modified if the company went bust. I think we used an escrow agreement once.
In more recent years, I've encouraged managers to pay extra for source code access or escrow. It costs money but you can turn software on and off -- with a bit more money, of course.