The premise is pretty clear: Binpress is a marketplace for source-code. Developers can buy and sell their code packages to each other.
Hey, they even have some WordPress-powered pieces of code, like WP Auctions, which is a bit weird since you can buy it directly off their own site here. I suppose Binpress doesn’t have an exclusivity clause.
Binpress is trying to change some of the perspectives of selling “open source” software: