Irving Wladawsky-Berger has a basic definition of open source (thanks to Ross for the link):

Now, when you collaborate with your colleagues, they have to be able to read and understand what you say, whether you use a natural language like English, or mathematical notation, or tables of numbers. Likewise, if the collaboration involves software, then you would expect to be able to read, modify and generally share the source code of the software on which you are jointly working. Thus, in my opinion, open source software is just a by-product of, or rather a necessary precondition for, collaborative innovation involving software. Nothing more, nothing less.

It’s much the same in Participatory Communications where software is replaced by language. As Ross points out, language lowers the barrier to participation. To which I would add technology as an enabler and precondition.