Basic GPL Question (Newbie Warning)

[Arnoud Engelfriet]

Kelly Anderson wrote:
> SpamAssassin is licensed under the GPL. It is obvious that it has been and 
> is permitted to incorporate SA into commercial products because there is a 
> commercial product page on the official SA home page. By one reading of the 
> GPL, if one uses GPL software to create a derivative work, the derivative 
> work must also be released under the GPL. 

There's no obligation to release the derivative work under GPL. You
are free to keep the derivative work a secret, as long as you use it
only internally in your organization. But if you want to distribute
the derivative work, then you have to do it under GPL and not any
other license.

So if I'm an ISP, I can modify SA to work with my mailserver and I
do not have to share my modifications with anyone. If I sell a
mailserver product, I have to give my customers the modified SA
with source code under GPL.

> (My understanding is that this is 
> the primary difference between the GPL and the LGPL.) 

The primary difference to me is that the LGPL is quite restricted
in the scope of what you have to make available if you distribute.
Under the GPL, anything "based on" or derived from the GPL-licensed
software has to be made available. This is often interpreted to
include anything linked to the GPL-licensed software as well.

Under the LGPL, there's no requirement to make anything linked to
this LGPL-licensed software available. So if SA were LGPL, I can
give you my mailserver in binary form, linked to SA, and I only 
have to give you the SA source code.

So I guess it depends on who is using and distributing SA and how.

Arnoud

-- 
Arnoud Engelfriet, Dutch patent attorney - Speaking only for myself
Patents, copyright and IPR explained for techies: http://www.iusmentis.com/