Bruce Perens (co-founder of OSI) has coined the term "[crayon license](https://lists.opensource.org/pipermail/license-discuss/2011-December/017416.html)":

> I've been calling these "crayon licenses", taking a line from an old Monty Python sketch about a dog license with the word "dog" crossed out and "cat" written in, in crayon.

The licenses referenced are typical well-intended free software licenses that have been written by programmers in simple, easy-to-understand, non-legalese language.  Some typical examples are the [WTFPL](http://www.wtfpl.net) and the somewhat more elaborate [Artistic License 1.0](http://opensource.org/licenses/artistic-license-1.0).

Perens seems to imply that such licenses may pose a problem for developers using them, or for the open source community.

How can these licenses be a problem?

Or is Perens wrong about them being a problem?