Postby sas » Thu Jan 05, 2012 8:53 pm
Unless I've misunderstood what you want to do, I don't see how there can be any problem here. You apparently have a licence for the font (it probably came with Microsoft Office, or something similar), and aren't intending to redistribute it or install it for use on a large number of computers, so the licence you have ought to be fine. And Cooper Black is so old that the glyph outlines (which is all that would appear on the T-shirts) are presumably out of copyright anyway.
But if you're really worried about it, you should ask on a forum frequented by type designers, who will be much better informed on issues of font licensing than anyone here is likely to be.