What's the basic difference between Linux and Unix ? I know that Linux was based on Unix (minix) and I suppose that many of the commands are the same, but is there a more substantial difference?
Unix is or was licensed by AT&T, so it is not really free, as in free speech. Linux (most of them anyway) is free, as in free speech and in most cases free beer. As far a technical difference. Sorry I really can not post it here right now.
as far as I know, unix only runs on a few platforms, its proprietary
other than that, all the unix standards apply to GNU-linux, everything is a file, all unix commands work, its multi-user, its based on and mostly written in C, etc etc etc
linux vs unix 
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