It's one license per computer. So you would have to either buy two licenses or get the Family Pack, which comes with five licenses.
If you're a student, check with your school for OS X licenses. Usually, you can buy a copy with the disc for $69 or less, and then buy individual licenses for pretty cheap (my school offers each license, without media, for $15). But if you don't qualify for an educational discount, then go for the Family Pack. It's much cheaper than buying two retail licenses ($199 compared to $258).