The 404 is "page not found", so we can't read the restrictions.
However ... the only restriction on the redistribution of GPL'd software that's possible is that it be GPL'd as well. That may be all that's implied by the comment.
Frank, can you clear that up? ACS 3x was GPL'd, as is OpenACS 5.0. We allow packages built on top of OpenACS 5.0 that doesn't contain our code to be licensed however one wants (much like a program running on top of Linux) but of course if your code contains any of our or ArsDigita's GPL'd code then it needs to be GPL'd as well.
