Basic GPL Question (Newbie Warning)

[Kelly Anderson]

Licence Gurus,

I apologize if this is a hashed over question, but I've found conflicting 
information online, (specifically at Wikipedia) so I thought I would 
solicit some input from this august group. First, let me say that I am 
totally clueless and confused, but well intentioned, so go easy on me. :-) 
I also apologize profusely if I have stumbled onto any religious issues in 
my profound ignorance.

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. (My understanding is that this is 
the primary difference between the GPL and the LGPL.) This obviously hasn't 
happened in most of these cases. Are the SA folks, and their users playing 
fast and loose with the GPL or is this the way the GPL is designed to work?

Another reading of the GPL would be that if you MODIFY the source before 
you use it, you have to release the modification. If this is a correct 
reading (I am not 100% sure) then would simply porting a GPL program to 
another computer language be considered a modification, and would you then 
be required to release the port under the GPL?

If you didn't release it under the GPL, would you be prohibited from using 
the port in your own programs?

Would you be permitted to charge a "distribution fee" for the source code 
of the port?

Thank you for your time, again, I hope that my clueless newbie self doesn't 
cause too much of a problem here.

-Kelly