Pretty impressive for any company, let alone a bootstrapped one. I'm really glad Peldi still makes these sorts of posts, a lot of times the openness disappears when the money starts coming in.
Broadly, it's a tool that enables others to build their own sites but also their own businesses (and I think entrepreneurs like supporting each other as it helps prove that the rewards do indeed exist). It lets users share, in a sense, in the success to be associated with a product they've used while also being inspired.
Of course, there can be a thin line between sharing and bragging/offending his user base, but I think he treads it quite well.