My understanding of those (thus maybe wrong) is, that they are built on too of third party licensed code and patents. Thus opensourcing is hard and would require reimplementation. Thus choice is this model or nothing. One could also create those modules as open source versions, but there doesn't seem to be enough interest by independent folks ...

There most certainly is a world of options between "all open source" and "aggressively litigious jerks".

https://www.theregister.com/2019/10/04/oracle_virtualbox_mer...

I don't care too much about it, but I wonder whether the open sourcing of it and the Enterprise license for commercial use requirement are really orthogonal.

Nothing is forcing Oracle to "routinely check log files for downloads of the VirtualBox Extension Pack from nonresidential IP addresses and contact unlicensed users to enforce compliance" (per https://en.wikipedia.org/wiki/VirtualBox#VirtualBox_Extensio...). They could easily just say "this software is free for commercial and non-commercial use."

One could also make it not ‘free to download but we might sue your enterprise if it’s used on your network’.

The choice is not ‘this model or nothing’, Oracle is about the only company this aggressive.