I wrote about this very subject a few months back:
"...I see no evidence that they try to shutdown the occasional hacker. Unlike the RIAA, Apple isn’t suing grandma because she had the wherewithal to get a Hackintosh running.
But there’s a world of difference between the average one-off geek assembling a Mac clone and a corporation (no matter how small) doing the work for you and making it widely available."
It's not so much Apple letting the Hackintosh community flourish as it is not being worth the effort to try to stop it. Apple's clearly smarter than the RIAA, though that's not saying much.
Why Does Apple Allow Personal Hackintoshes?