If I download a freebie (from here or anywhere else) that either doesn't have a readme file or has one that doesn't mention usage restrictions at all, is it legal for me to use the item in a commercial render?

What if I create something for personal use, show it for personal use, but sometime in the future a commercial opportunity comes up and someone wants to include "my creative works" in something for sale?
[yeah, like that's going to happen to me]

Before they made me they broke the mold!
http://home.roadrunner.com/~kflach/