I equate Open Source with collaboration in the public (which includes people using the software but maybe not contributing), but I also think that Open Source can only be thought about clearly in terms of licenses.
For example, suppose I wrote a piece of code and throw it out to the world without saying anything about the license. It catches, and a bunch of people start using it and contributing. Awesome! Collaboration!
Then Macrosoft comes by and says, we’re going to take this software, package it up, sell it, and not credit you or pay you. And now I’m thinking, ok I should have maybe said the source is free (as in freedom) for use but you should check with me before profiting. Also, not crediting me isn’t cool.
Then some jackass comes by and extracts some comment I wrote, excerpts it, then prints it on t-shirts they sell to support a hate rally, and attributes it to me. Again I’m thinking, ok maybe I should have said that you can’t claim I endorse anything you do with my code.
Then the government comes by and takes my code and sticks it into a drone which bombs a little town in some war region, and then all of sudden a bunch of militants are blaming me for the destruction of their homes. And I’m thinking, ok maybe I should have said that I’m not responsible for the actions of people who use my code.
And I could complain vocally about these things, maybe even assert that github should remove all my repos because, well, I don’t like the actions of the life sucking Macrosoft lawyers, and still say that I’m open to collaboration. But Macrosoft would come back to me and say their idea of collaboration isn’t the same as mine, and the jackass would come back to me and say their idea of collaboration isn’t the same as mine either, and the militants would say that I collaborated with US imperialist warmongers and thus deserve to be dead.
Whatever definition of Open Source you use, if you haven’t thought carefully about the expectations of people using your stuff, then you haven’t thought carefully at all. If you do think carefully about people using your stuff, then what you’ve done is created a license. In my view, a definition of public collaboration on software is one and the same as a license, and so I define Open Source entirely by its license.