Indie Books are books published outside of mainstream publishing. You're misrepresenting what Indie Books are with your own opinion of what you want to see on the site instead.

If the books are books for developers, then by now it's clear that they will be sold online. What effect does "mainstream publishing" have on publishing material on the internet? It's the internet. There is 0 meaningful difference if a book has mainstream publishing if both books can easily be listed on Amazon, Ebay, or anywhere else, because it's the internet.