Open Source and Collaborative
Collaborative means done in a way that allows any other qualified developer to contribute to a project, with minimal friction in the process.
Many technologies that are open source are not developed collaboratively. The typical model is: a small team develops, and releases when done. There are 2 issues with this: (1) design is not generated collaboratively. 2 - since a project is 'never done', collaboration from the onset is more likely to produce a working product at all.
Outside of usual open source project, the City of Encinitas ADU is a great example of an open resource that is developed non-collaboratively.
Many collaborative technologies (such as Google Slides) are not developed collaboratively, and are not open source. They may be free, but they are missing the 4 Freedoms of Open Source.
In summary - open source AND collaborative are not the same thing. OSE emphasizes open source AND collaborive as a prerequisite to solving Pressing World Issues - and thus requires both aspects to be present in order for fruitful collaboration to exist.