Thank you Daltonik for sharing those bonus codes with us!
The first code ($3) is still working. I just redeemed it and $3 were instantly credited and added to my USDO balance. Unfortunately, the $12 bonus code (12NOW) has expired. Anyway, if you claim the free $12, the maximum you can withdraw from your winnings is only $25 (according to the article you linked) but it's still free money so can't complain.
The only inconvenience is that you can play with your winnings from free spins only on the bonus mode which has a small number of games.