Even if you give "free to good home" there are things that clue you in to whether or not a person is affiliated with a lab. This is a paraphrase of a call I had on my machine when I had some fosters up for adoption. Keep in mind my ad in the paper did not specify age, color, or sex:

"I saw your ad in the paper for free kittens. I need those kittens. Call my pager at 555-1212"

Clue #1-no inquiry into colors, ages, or sexes available
Clue #2-no name or home phone number given
Clue #3-"needing" the whole litter
Clue #4-taking the whole litter without knowing if that meant 2 or 8 kittens

Spencer-from what I was told in the new employee orientation a few weeks ago, UTSW no longer does animal research (but you know how that goes, that does not necessarily mean it has actually been discontinued). I will try to find out more.