That particular clause has caused quite a bit of headache for PHP package maintainers, because technically it makes the license a non-open source license, even though the rest of the license is just your bog standard MIT/BSD-like license.
Long story short, don't write your own licenses.
see e.g.: http://wonko.com/post/jsmin-isnt-welcome-on-google-code
Would it be Discrimination Against evil Fields of Endeavor?
"It's evil, fercryingoutloud! Don't do evil!
Everyone knows what evil is!"
And it gets used, and that clause sits there, like a hidden dog turd, waiting for someone to step in the wrong spot, and all of a sudden the developer and their minions are up in arms about the user and their minions, who are so obviously evil that there shouldn't even be a discussion.
Because it's evil, and evil is self-evident.
Except it isn't. It really, really isn't.