I first encountered the smile license when looking for a markdown driven CMS and stumbling across Anchor CMS. The license came with the following message:
Congratulations, you’ve got something with the best license ever.
Basically, you’re free to do what you want with it; as long as you do something good (help someone out, smile; just be nice), you can use this on anything you fancy.
Of course, if it all breaks, it’s totally not the author’s fault.
Enjoy!