Where can I use these sprites? (Copyright)

[Jaret]

I want to develop a small browser game using ripped-off sprites.
I see a lot of people using the resources on this website for this exact purpose.

But aren't the owners of the copyrights suing people that make a game using their assets?
And what are the conditions under which these resources can be used? Free of course but other than that, can they be available for download, or put on a website?