GPL and dsitribution of source code

[Jan Wildeboer]

Hello list,

I would like to have some sort of official statement on the following 
question:

When I distribute a program under the terms of the GPL I am allowed to 
ask a fee for this. Though the recipients/customers are entitled to 
distribute what they get from me for free or not, I can ask for money to 
distribute my program.

Then there is the GPL 3b

  b) Accompany it with a written offer, valid for at least three
     years, to give any third party, for a charge no more than your
     cost of physically performing source distribution, a complete
     machine-readable copy of the corresponding source code, to be
     distributed under the terms of Sections 1 and 2 above on a medium
     customarily used for software interchange;

That clearly says I must give the sources for my application for a very 
low fee or for free.

My question is - if the general format of my application is source code 
(PHP for example) must I then give the sources according to this part of 
the GPL or can I ask for any fee?

Background: I am involved in a GPLed project and we have decided to 
distribute our application for free. Some companies have programmed 
add-ons for our application and are not willing to give us the sources 
for free. They distribute the sources (PHP programs are normally 
distributed as source files as it is an interpreted language) for a fee, 
for example $280.

Is that allowed? Or can I ask them under the terms of GPL 3 to send me 
the sources for the physical costs?

Another question - directly related. If a company has modified our 
program and we ask them for the sources - can they say: We have to 
update the sources to delete the customer related data and that will 
take 20 hours at $70 an hour so pay $1400 to receive the sources?

This is a very important question for me and our project. Please help.

Jan Wildeboer