I am not really copyright-sensitive.
You might as well do anything you wish with anything you find on this site: feel free to download, use, or modify any of the stuff I have put together here.
Yes, you can take the CSS framework too. You can use your own creativity to build any design (even a not-so-outdated-looking one like this) based on it. This version I wrote is much simpler than the standard bootstrap.
I don't even insist on being credited, just don't claim the stuff to be your own.
I don't really see how this stuff could possibly be used for any commercial or financial gain, so I don't even mention anything in that direction.