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Basic licensing etiquette (was Re: GPL)

Derek Haines (derek.haines@gmail.com) wrote:
> I've been having a hard time finding answers to the following GPL
> questions (can anyone here help?) :
> I write a piece of software from scratch and release it under the GPL.
> At the top of my source files, I have a standard copyright notice:
> Copyright (C) 2005 Derek Haines
> (as well as the GPL notice). 
> If someone (e.g. John Smith) modifies a source file by adding or
> changing lines of code, do they and/or should they then add a
> copyright notice:
> Copyright (C) 2005 John Smith 
> in addition to my original copyright notice? (Making
> Copyright (C) 2005 Derek Haines
> Copyright (C) 2005 John Smith 
> or some variant available in the same file).
(followed by the GPL licensing notice, of course... see below.)
If the change is significant, they can and they should.  (If they don't, it 
can lead to problems later if anyone has to do a licensing audit.)
If the change is insignificant, they shouldn't, but it normally doesn't hurt.

Incidentally, the (C) is worthless and should not be used.
Just write "Copyright 2005 Derek Haines".

> Can they remove my original copyright notice?

> The
> definition in section 0 of "work based on the program" as in part "any
> derivative work under copyright law" may protect against someone
> removing the original copyright, if there's a provision in the law
> against removing copyright notices.

> Is there any protection against 
> removing prior copyright notices?
The principles of derivative works.  Suppose the original work is A, by you, 
and the derived work is B, by John Smith.  B is a derived work of A because 
it contains large portions of A.  B is considered to be subject to *two* 
copyrights; your copyright, and John Smith's copyright.  Permission is needed 
from both you and John Smith.  The header featuring both of your copyright 
statements, and the GPL permission grant, gives that permission.  A header 
featuring only one copyright statement, would only give permission from one 
of you.

This belongs in a FAQ.

> I assume on the modified file I have copyright on the portions that
> are still mine and they have copyright on the portions (modifications)
> that are theirs. (Still all covered under the GPL). Is that correct?
Essentially, yes.  The portions can be inseperable though.  The classic 
example is a translation of a novel: the translator has a copyright on the 
translation, while the original author has a copyright on the original text, 
which is considered to be present, sort of, in the translation.

Certain types of code alteration are similar; if John Smith's changes ended up 
changing every fourth line of code in an interesting and creative way, for 
instance, it would be very hard to pull out "just the modifications".

> If so, does that protect against someone removing the original
> copyright notice (through general copyright law, whatever that is) ?
Yep, you've got it.  :-)

The same principles apply to code under *any* license.
If different parts of the code are under different licenses, then the license 
header might look like this:
Copyright 2005 Derek Haines
Copyright 2005 Jane Doe
These authors' portions of this work are available under this license:
(GPL standard blurb)
Copyright 2005 John Smith
John Smith's portions of this work are available under this license:
(MIT/X11 standard blurb)

(Notice that this is clearly allowed as a single derived work because MIT/X11 
is GPL-compatible.  If John Smith's portions can't be separated out, it 
doesn't really matter; if they can be, he might want them to be licensed more 
loosely for some reason.)

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