Earlier quoted context omitted.
Doesn't seem to be open source: https://github.com/craftcms/cms/blob/develop/LICENSE.md
It doesn't have to be open source to be successful. I understand that open source things can increase reach of the product, but that's at the expense of proper software support. Let's accept some proprietary software in our lives. Sometimes these have demostrated technical superiority.
Lots of open source projects offer premium support.
> Let's accept some proprietary software in our lives. Sometimes these have demostrated technical superiority.
Sure, but let's not pretend proprietary vendors know more than open-source projects and contributors. Also, if your product is ultimately the content itself, it's an enormous risk to hand that over to third parties that want to take control of it. You are explicitly coupling yourself to the success of the proprietary software vendor.