If open source projects change their licensing to force paying for business use and the cloud giants doesn't want to pay, the cloud giant could afford forking the project and make their own version.
This could lead to the original project being unmaintained and the new fork becoming the standard, if that happens and given enough time, the cloud giant can make software patents on the changes they've committed and change the license of that code/features. Making it even harder to create something similar or even something new with the same features.