I'd like to download a texture, but I can't find any licensing information. All that it says is "Free to use for commercial and non-commercial works." Which is nice, but imprecise. Is that with or without attribution?

Well, looking at some of the other stuff here I do see licensing information on some of it. I guess it's just a little inconsistently enforced, or this particular texture is too old or something. Is it safe for me to assume that this is public domain?