OpenSource generally means software that is probably free and allows anyone using it to modify it and post the modifications for others to use. Great example: Linux!
See Wikipedia for more on Open_source.
More from JerrittCollord:
"Open Source" is a trade or service mark owned by the Open Source Initiative at opensource.org, which is backed by people like ESR, Perens, and Ian (debIAN) Murdock. Various licences can be technically called "Open Source" via this body's "OSI Certified Open Source Software" acceptance process. This OpenSource is a movement that the Industry came up with to broaden the dialog between the Birkenstock coders and the Brooks Brothers business guys when everybody had to sit down together back in 1998-1999. One side honestly concerned about the well-being of the universe, the other side really concerned about the intellectual property they were sponsoring and want some ownership over. The two fundamental forces in nature.
RMS often says he doesn't know what this 'Open Source' is because he and the FSF have a more stringent term and definition they adhere to called FreeSoftware. The differences between the GPL and the BSD licences exemplify this greatly, read them for yourself and see. Old and not very bitter conflict, somebody drags it out now and again like an old blind dog and beats it just to hear it yelp. Most people just use whatever software works.
A clarification from RussellSenior:
The main argument for the term 'open source software' is that 'free software' makes some people uneasy. That's true: talking about freedom, about ethical issues, about responsibilities as well as convenience, is asking people to think about things they might rather ignore. This can trigger discomfort, and some people may reject the idea for that. It does not follow that society would be better off if we stop talking about these things. -- RMS
The hope is to use as much Open Source software as possible (and oh, it's more than possible but mostly necessary) in building the network, including packaging extant works into easy-to-install embedded functional units for the semi-end-user. Also, ultimately this network hopes to offer services that frankly are only accessible in any timely sense with Open Source operating systems over functionality that is standard in them e.g. IPv6.
In the PersonalTelco setting this probably means our driver thingies and protocol whatchamacalits will be freely available for use and modification. I'm sure AdamShand can give you much more details, it's just that the bright red wiki word on the front page was driving me nuts.