If "Uno" is a trademark and the game is near identical then you won't be OK, free or not.
I couldn't even call my snooker game "World Snooker" - the WPBSA threatened me with lawyers if I didn't change it - and that was only for a work-in-progress game.
Don't assume they won't bother with you - there's a strong possibility that they will. As Edzup said, they'll prosecute you for loss of profits and although that will be for a lot, they'll expect you to pay for the cost of the legal action as well, and their lawyers aren't going to be cheap.
I couldn't even call my snooker game "World Snooker" - the WPBSA threatened me with lawyers if I didn't change it - and that was only for a work-in-progress game.
Don't assume they won't bother with you - there's a strong possibility that they will. As Edzup said, they'll prosecute you for loss of profits and although that will be for a lot, they'll expect you to pay for the cost of the legal action as well, and their lawyers aren't going to be cheap.