Quoting mark burdett <mfburdett@gmail.com>:
Well I was just regurgitating http://www.gnu.org/philosophy/license-list.html which describes PHP License as incompatible with GPL. I do have my own "readings" of the various licenses, IP law, etc. but won't waste the list's time ;)
I suppose because of this <blockquote> 6. Redistributions of any form whatsoever must retain the following acknowledgment: "This product includes PHP software, freely available from <http://www.php.net/software/>". </blockquote> Which is in direct conflict with this <blockquote> 3. The name "PHP" must not be used to endorse or promote products derived from this software without prior written permission. For written permission, please contact group@php.net. </blockquote> because you cannot do 6 without it being considered an endorsement and you would need permission from PHP. Earnie P.S.: How is it a waste of developers time to understand the legalities of what they agree to license their copyright with?