Triton DataCenter[1] is open source[2], and has commercial revenue in excess of $1M ARR. We were fortunate to acquire this product from Joyent earlier this year[3], and are now well on our way to the next revenue target.
Triton was built on the backs of giants -- so a slightly different scenario than most.. But it is clear that customers will pay for open source products, and you can more than pay your rent one day!