[lug] Licenses: Apache vs. GPL

[Scott A. Herod]

Hello,

  I need to provide a client details of the licences of software that
I am using in a product I am working on.  I think that I am okay 
except for the possible inclusion of Xerces which is licensed under
the Apache license.  Stallman says that the Apache license is
incompatible
with the GPL license.

http://www.gnu.org/licenses/license-list.html#GPLIncompatibleLicenses

It seems to me, however, that the only complaint is the following 
statement in the Apache license:

The end-user documentation included with the redistribution,
if any, must include the following acknowledgment:
  "This product includes software developed by the
   Apache Software Foundation (http://www.apache.org/)."

Does someone know any references that a lay-person such as myself 
might be able to understand on why the above statement is an issue?

Thanks,

Scott Herod