Even further than that as far as I remember. They first had google adsense, around the time freebitco.in started there were a lot of faucets going around, they made their money from the ads and they gave a bit of it back from faucets and it was the perfect idea of getting free adsense income, you would get 100 bucks adsense income and pay 50 bucks of it back in faucet form and you would keep the 50 bucks back. Freebitcoin wasn't like that exactly, they had the gambling part as far back as I can remember but this was the situation in other faucets.

When adsense closed it for faucets, they went with ad networks, and they got offers, like an auction, whoever pays the most would get the ad on freebitcoin, and they got a lot of money for that time being as well, now looks small but it was a great deal for them at the time. After that they removed it, but there were another small time period between the adsense closing and freebitcoin removing ads, and that period was ad networks.