You can’t use the images, audio and those other stuff they used in the demos, but the code (the whole script) can be used in themes.
You can but you’re not required to put a link to the tutorial somewhere, perhaps the item description.
1st line of license:
The resources on Codrops can be used freely in personal and commercial projects
You are allowed to create templates from the resources on Codrops if you integrate them or build upon them.
You are not allowed to take our work “as-is” and sell it, redistribute it or re-publish it.
That last sentence means basically that you can’t just copy exact and sell as is (ie the same thing they give as a download) or give away for free.
So it’s very clear you can include in your commercial product for sale as the code they provide for free has been integrated and built upon by yourself.
PS – TF is just FULL of every new codrops code snippet.. ugh.