use of the kernel and licensing

[Steve O'Hara-Smith]

On Mon, 01 Apr 2013 10:26:15 -0400
Joe <fbsd8 at a1poweruser.com> wrote:

> snip....
> 
> How do you explain all the forks of UNIX each claiming their own 
> copyright.

	Look very carefully at the copyrights involved, you will see
copyright attributions retained very carefully (see for example the
file /usr/src/COPYRIGHT in FreeBSD).

> They all provide the same concept, use the same names for 
> their commands, use the same programming language, have a filesystem as 
> their base.

	These features are defined in open standards (POSIX and SUS) for
anyone who cares to implement them.

> Just where is the line drawn between a fork and a rewrite?

	That's simple in essence, if it's written by taking a copy of the
code and modifying it then it's a fork (until and unless you can prove that
not one single line of the original code remains), if it's written from
scratch with no reference to the original code then it's a rewrite. I
suppose there are edge cases where a rewrite may include a portion taken
from the original (assuming compatible licensing), or where a fork has been
so heavily modified that little of the original remains.

-- 
Steve O'Hara-Smith <steve at sohara.org>