Basic GPL Question (Newbie Warning)

[Ruth A. Kramer]

Arnoud Engelfriet wrote:
> 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.

I haven't looked at the SpamAssassing page / license before making this
comment, but there is another way (iiuc) that commerical / proprietary
version of SpamAssassin could be offered without violating the GPL and
not requiring that modifications be shared etc.  The original author(s)
/ copyright holders of the SpamAssassin code could dual license it,
making a (presumably free or low cost copy) available under the terms of
the GPL, and selling (presumably at higher cost) a copy under a
different license.  

There could be "real" differences in the programming of the two copies
(versions) or they could be identical except for the license.

IANAL.

Randy Kramer