Off the top of my head: https://en.wikipedia.org/wiki/MaxDB#Licensing https://en.wikipedia.org/wiki/MaxDB#Licensing In case of Microsoft, you don't even have t

Off the top of my head: https://en.wikipedia.org/wiki/MaxDB#Licensing https://en.wikipedia.org/wiki/MaxDB#Licensing In case of Microsoft, you don't even have to be very imaginative: how much of the stack currently in use by .Net developers on Windows is completely open? How important and hard to replace are the parts that aren't? And how much of a difference would it make in the end to have had Core open source in the past, when the new and closed version is the only one that works with those billions of Windows10 tablets and those popular Azure services that everyone needs for their startup?