I have been reading about *nix history and the more I read the more I get confused.
I am reading terms like
... is based on ...
or
... and ... derived from ....
etc.
A concrete example from Wikipedia:
Berkeley Software Distribution (BSD) was a Unix operating system derivative developed and distributed by the Computer Systems Research Group (CSRG) of the University of California, Berkeley, from 1977 to 1995. Today the term "BSD" is often used non-specifically to refer to any of the BSD descendants which together form a branch of the family of Unix-like operating systems. Operating systems derived from the original BSD code remain actively developed and widely used.
So what is a derived operating system ?
53 Answers
These phrases mean the same thing they mean in other contexts, and they are just as subjective in this context as in others.
If a new car model is based on an old one, then some part of the old design was used in some fashion, perhaps directly, perhaps modified, perhaps just as an inspiration, when designing the new one. If a fictional story is based on a true story, same idea - fictional story inspired by and containing many similar elements, some maybe modified, as original true story. Etc. Same with "derived from", although that usually implies the case of "based on" where modifications were done to the original (with some extras).
So if OS B is based on A, some unknown significant amount of things from A were used when B was created. Perhaps code, perhaps user-interface design, perhaps philosophies, etc.
An opposite of sorts is starting from scratch. If B is some brand new concept, designed from the ground-up with no major source of inspiration and no components from A, then B was neither based on nor derived from A.
There are no strict definitions of the terms you describe, but what they often mean:
"Derived from" often means a fork somewhere along an operating systems development cycle. Say, someone liked what Ubuntu had to offer, but decided to make their own version, and thus Linux Mint was born.
"Based on" is a bit more loosely used. Many would say that Linux is based on Unix, but linux is in no way a unix-decendant, in that linux was written from scratch, inspired by the functionality. In away, you could also say "Inspired by" and be just as correct.
As for the specific example you mentioned, BSD did in fact fork multiple times. Today some of the most well-known ones are NetBSD, OpenBSD, and FreeBSD, of which the latter I've been using a lot. These can be considered to be Derived From BSD, as a group of individuals independent from the BSD core team decided to roll their own OS, starting out with BSD and its source tree.
4"based on" means similar functionality. Linux is based on Unix because it aims to the same way of work.
derived from means that it uses the same basic tools. For example, Ubuntu is derived from Debian. Ubuntu uses the same fundational tools of Debian adding some of their own.
