i'll always concede that these technologies are extremely relevant in the web backend space, but for the most part their are bizarre curios that some technical people know about and even fewer actually use.
gcc has done okay, and its a fantastic project in many ways... some of the optimisations its capable of are really quite smart. that being said though it has usually been held up as example of how hairy compilers can be. there was a period where gcc saw some real use from apple and sony, but other than that its always been considered the outsider in practice... at least during my career. maybe in the dark and distant past when it was even harder to use GNU/Linux and Unices then it compared favorable against borland and the ms vc 5 compiler... but i doubt that is true.
I'm never going to be onside with licenses like GPL when there are MITs and BSDs which do not impose draconian restrictions to help further a philosophy instead of being actually free. The single most common reason I hear not to use a library, borne from practicality, is that it is GPL or LGPL licensed.
The fact that you cite something that, to a close approximation, nobody has heard of as an example of how this stuff has made the world better is a brilliant example of what I am talking about.
Open source is great in lots of ways, but I'm convinced it would be better if its proponents and contributors were a little more in touch with reality.