The license is called "Developer license" which I at least associate with multiple use, and I don't see them specifically mention "single use only" (although I see that the text can be interpreted that way) .. http://designmodo.com/startup-license/
EDIT: got a reply from them on twitter: https://twitter.com/Designmodo/status/412867217118605313
You were right: "one license - one project."
Being a non native speaker, I had no doubt that a developer licence saying "You have rights for royalty free use of our resources for any of your personal or commercial project." lacks the pluralization of project and is meant to allow using it on _any_ of your projects. Designmodo clearly stated it's one licence for one project. They should replace _any_ with _one_.
It looks lovely, no doubt about that, but for a $249 single-use license I would expect it to be backed up by bulletproof code. If that website is an example of what you end up with, it's not.