I would maintain though that in the old days folks did this because they didn't HAVE the "money" to do this sort of thing and needed help in raising a barn, for example.
I hold that what motivates folks to contribute to open-source is a lot more complex, since in many cases folks contribute more as a hobby than expecting a tangible reward such as quid-pro-quo, although no doubt the idea of "giving something back" is very strong if one has gotten good use of some piece of open-source software in the past...
Sure it is, given the hugely larger number of individuals involved. I suspect one can find an example of virtually every "motivator" that exists with some individual or other--I simply point out the "barn-raising community" aspect as one possibility among many.
A lot of folks (Coral Snake being one) seem the have the idea that the American colonial/republic phenomenon was mostly about capitalism, which it is not. Both individual AND "communal" approaches have existed side-by-side from the beginning. Unfortunately, many of the "communal" approaches (citizen militia, local school boards, etc.) have been largely co-opted by government--but there are STILL come out there (see any bake sale for a school/church group).