Applications vs Libraries
Applications have always had a somewhat uneasy relationship with open source licensing. This is in part because an application is so much more than the code.
An end user focused application like Wordpress implies a commitment to support, to plugin repositories, building an ecosystem. The problem of course is that the license itself implies none of these things.
And so, open source applications find themselves in a weird tension. The demand to provide services of various sorts far beyond what's committed to in the licensing. Creating a need to create revenues on top of a product that provides very little lock in. Anyone can take the code and make hosting for it, or provide services around it.
An open source code library is very different. Most of the time the only implied commitment of a library is the code. Nobody expects an ecosystem around a string helper.
Even moving up orders of magnitude, libraries like SQLite are used on billions of devices without even so much as an official conference.
This is why we've seen large open source applications tend to move towards some kind of commercial licensing over time. SugarCRM, Mongo, Elastic, Redis, etc.
Users/customers of these applications demand stability, ecosystems, support. They want the commercialization of the software.
Given that, I wonder if some kind of commercial licensing (maybe a dual license) of Wordpress may have been a more stable approach to Automattics apparent desire to more fully monetize Wordpress.