[R] Taking code from packages

[Duncan Murdoch]

On 1/13/2006 2:04 AM, Ales Ziberna wrote:
> Hello!
> 
> I am currently in the process of creating (my first) package, which (when
> ready) I intend to publish to CRAN. In the process of creating this package
> I have taken some code form existing packages. I have actually copied parts
> of functions in to new functions. This code is usually something very basic
> such as Rand index. What is the proper procedure for this?
> 
> Since most of R (and also the packages I have taken code form) is published
> under GPL, I think this should be OK. However I do not know if:
> 1.	I should still ask authors of the packages for permission or at
> least notify them.

It is polite to notify them.

> 2.	Ad references to the functions (and packages) from which I had taken
> the code or only to the references they use.

The GPL requires that you maintain their copyright notices.  You have 
the right to use their work, the GPL doesn't give you ownership of it.
The usual way to do this is to leave their copyright notice intact, and 
add your own if you have made modifications.

An alternative which is usually (but not always) better is to say that 
your package depends on theirs, and then just use their functions.  The 
advantage is that it avoids any of the above mixed copyright issues, and 
it makes sure that when the author fixes a bug, you benefit too.  The 
disadvantage is that it makes your package dependent on theirs, so if 
changes are needed in it for some future version of R, you'll have to 
wait for the other maintainer to do them (or copy their code at that point).

(I'm a little sensitive about dependencies now, since the LaTeX seminar 
template I've used a few times no longer works.  It depends on too many 
LaTeX packages, and someone, somewhere has introduced incompatibilities 
in them.  Seems like I'll be forced to use Powerpoint or Impress.)

Duncan Murdoch

> 
> What about regarding code that was sent to the list, usually as a response
> to one of my problems. I assume that in this case it is best to consult the
> author?

> Any comments and opinions are very welcomed!
> 
> Best regards,
> Ales Ziberna
> 
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