The terms of the GPL are clearly spelled out and have a legal meaning that people have tried very hard to make unambiguous. The Free/Non-free debate happens outside of the interpretation of the rules.

If I made a license that said: "You may modify and distribute this so long as you do not violate the spirit of Free Software", then I've made an ambiguous license like Crockford's, where it seems like I could probably withdraw permission from anyone for any reason that suits me, at any time.

If you have a license under terms that are unclear - you don't really have a license. In some contexts that will made a difference to you, and you'll have to find some other solution than to run this software.

But as a piece of performance art, I think Crockford's license is brilliant.