>and then one of their whizz kid programmers modifies the OS so now my app doesn't work anymore, who is legally liable for this?<
If Microsoft makes a new OS that breaks your program, are you going to sue them?
On the practical side, just blow your customer off like all the other software companies do. ("this program does not support unstable kernel versions", or the like)
Most of you are approaching the Open Source philosophy backwards. You're saying, "Why give away your hard work?", when in reality, the question should be, "Why not split the effort with other volunteers?". Most Open Source people actually *enjoy* coding(a difficult concept if you do it for a living instead of as a hobby). And the coding they do, they do because they need some feature that isn't available in a product that is within their price range(or isn't available at all).
They're not giving away their hard work--they're allowing the other kids on the beach to play with their sandcastle.
>i mean to say, the average of the condition of the world can be improved if we go the lesser countries and get them up to speed...<
It would take three earths to supply the entire world's population with enough resources to bring them all up to the US's standard of living.(at least with capitalism/consumerism)