\\

Please write ``source for product $Y$'' in the memo line of your

payment.

You may also find a copy of the source at

\verb0http://www.example.com/sources/Y/0.

This offer is valid to anyone in receipt of this information.

\end{quote}

There are a few important details about this offer.  First, it requires a

copying fee.  GPLv2 permits ``a charge no more than your cost of

physically performing source distribution''.  This fee must be reasonable.

If your cost of copying and mailing a CD is more than around \$10, you

should perhaps find a cheaper CD stock and shipment method.  It is simply

not in your interest to try to overcharge the community.  Abuse of this

provision in order to make a for-profit enterprise of source code

provision will likely trigger enforcement action.

Second, note that the last line makes the offer valid to anyone who

requests the source.  This is because v2~\S~3(b) requires that offers be

``to give any third party'' a copy of the Corresponding Source.  GPLv3 has

a similar requirement, stating that an offer must be valid for ``anyone

who possesses the object code''.  These requirements indicated in

pass these offers along with their distributions.  Therefore, the offers

must be valid not only to your customers, but also to anyone who received

a copy of the binaries from them.  Many distributors overlook this

requirement and assume that they are only required to fulfill a request

from their direct customers.

The option to provide an offer for source rather than direct source

distribution is a special benefit to companies equipped to handle a

fulfillment process.  GPLv2~\S~3(c) and GPLv3~\S~6(c) avoid burdening

noncommercial, occasional redistributors with fulfillment request

obligations by allowing them to pass along the offer for source as they

received it.

Note that commercial redistributors cannot avail themselves of the option

(c) exception, and so while your offer for source must be good to anyone

who receives the offer (under v2) or the object code (under v3), it

\emph{cannot} extinguish the obligations of anyone who commercially

redistributes your product.  The license terms apply to anyone who

distributes GPL'd software, regardless of whether they are the original

distributor.  Take the example of Vendor $V$, who develops a software

platform from GPL'd sources for use in embedded devices.  Manufacturer $M$

contracts with $V$ to install the software as firmware in $M$'s device.

$V$ provides the software to $M$, along with a compliant offer for source.

In this situation, $M$ cannot simply pass $V$'s offer for source along to