They make money from transaction fees and from mining.
I wouldn`t say that freebitco.in is a faucet site.It`s a bitcoin gambling site.
And yes,freebitco.in is legit indeed.
They have several methods to generate income to distribute to users. They started out with gambling and advertisements and now they added a
mining operation that generate income too... They use all of this to pay themselves and also to pay their faucet users. People can also "bank"
money with them and they get interest on those deposits. { they use this money to fund their hardware and overheads to expand the mining
operation }