Choosing the right license

[Charlie Stross]

I need an open source license; trouble is, I don't know whether one
that suits my specific requirements already exists or not. Here's the
situation; do any of you guys have any suggestions?

A friend and I intend to write an application that has some commercial
utility. In particular, similar software is used by a number of ASPs
who charge their customers on a per-usage basis. 

What we want to do is make our application available under a license
that complies with the open source definition (as a minimum -- the
FSF's definitions would be better), but that makes it difficult for a
commercial entity to charge third parties for the use of the software.
That is: there should be no problems for a business using the application
for its own internal use, but it should be difficult to charge customers
a fee for using it as a service.

Do you know of any open source compliant licenses that accomplish this,
i.e. make it difficult to sell the use of the software, while remaining
open-source compliant?

Nearest thing I can think of is to start off with the GPL, then add a
rider along the lines of "if you sell this software or derived works, or
if you sell any service based on this software, then with every fee-
carrying transaction you must notify the customer of the full text of
this license, including the phrase IF YOU ARE PAYING FOR THIS SERVICE
YOU CAN GET THE SOFTWARE THAT SUPPLIES IT FOR FREE AT http://somewhere/".

In addition the license needs a rider along the lines of "this software,
as supplied, has been certified for connection to the XYZ proprietary
networks; if you modify it you acknowledge that you are breaking the
terms of this certification and are no longer authorized to connect to
the XYZ networks under the original certificate of compliance".  But I
figure this should be fairly straightforward.

Any suggestions?



-- Charlie