To quote the site:

You may use the sound effects on this web site free of charge in your video, film, audio and multimedia productions (but do not re-sell them or post on a web site for download).

I have considered Blocks From Above! a multimedia production. Whether or not that was the right thing to do is questionable, but in my opinion I have credited them sufficiently to make up any possible ”violation”.

I have indeed posted their sound effects on a web site for download, but I have done so in an extremely indirect way (included in a game). Besides, sound effects can be copied from videos too, so there’s no real difference.