Why GNU/Linux, part 2

Some started to use linux out of curiosity, some because they had enough of the restrictions of other OS they were using, some didn't have computer with performances to run some other OS smoothly, some wanted to have a stable system, to have it for free and so on.

It is well know that most (93,8 % in Nov 2012) of TOP500 supercomputers are running on Linux.

NASA recently migrated to Debian GNU/Linux on their International Space Station (read about it here). Why? As Keith Chuvala of United Space Alliance said, "(...)because we needed an operating system that was stable and reliable – one that would give us in-house control."
More and more municipalities (like Munich) and goverment agencies (like French National Gendarmerie) are also migrating to some of linux distributions. Why? Because that costs them a lot less money.