Take Hashicorp's Terraform as an example. Until recently, the code was completely open source with a permissive license. You could do exactly as you like with

Take Hashicorp's Terraform as an example. Until recently, the code was completely open source with a permissive license. You could do exactly as you like with it. The 'single vendor' decided that was no longer in their best interests. What's the problem? Now you have 1000's of companies that rely on this software, and if they want to continue to receive security updates, they need to comply with the new license. Of course, people are free to fork projects, and that has been done in the case with terraform, but it's something that a foundation-led project most likely wouldn't do (change the license). There's another flavor of single vendor open source IMO. I call it 'look but don't touch open source.' Modern software projects have become some complex, and the build and dependency systems so customized, you could have the source code available, and be free to modify it, but wholly unable to do so because of the build-time complexity. A foundation-led project would, ostensibly, ensure that the entire lifecycle of the software is approachable by end users (docs, tooling, etc).