He should have always been (trying to be) aware of all the licenses he was using from the start. You can't just use any code you find on the net and staple it into your project.
And that says nothing of the commercial products I licensed that I knew I wouldn't be able to sublicense. But, the name of the game was expediency. I liked the theme on WrapBootstrap. I paid ~$20 for it and got up and running in a weekend. Recreating that would have been considerably more effort at significantly more cost. I made a trade-off, as businesses need to do. It's technical debt, one I'm not obligated to pay and don't see the long-term value being worth it.