You are of course allowed to create videos using any of my games: previews, reviews and “Let’s Play” videos are all welcome! You can publish these videos to your website, YouTube or any other similar video sharing services. You are also allowed to monetize these videos via the YouTube partner program and similar programs on other video sharing sites.
Sometimes I use free content (mostly music & sound effects) in my games; In such cases, attribution is given to its respective author in the credits page of the game, and it would be really nice of you if you credit them in the video description as well.
It would be even better if you put a link to this website anywhere in the video description too!
And finally: don’t forget to let me know of your video when it’s online, I’d love to watch it! 🙂