My baby is 10 weeks and boy he farts like an old man. He is also formula fed.
To answer you, it's perfectly normal for babies to fart too. And sometimes they're gassy when they swallow a lot of air during feeds. If your baby is bottle fed like mine, pay attention to how they're fed and the nipple size. Burp the baby during and after each feed to get rid of trapped air. But farting helps them get rid of gas, so it's good when they fart. Trapped gas leads to lots of crying.
My baby's poop at 4weeks was yellow too but not foamy.
It wouldn't hurt to get him checked by a paediatrician. But foamy poop is usually a result of baby getting too much lactose from breast milk.