To me, the only interesting things that could be in a pistore like that are alternate distros (piplay, rasplex, retropie.. etc)

the open pandora had way more success with an 'app store', because it had a uniform interface and niche community formed mostly around gaming.

http://repo.openpandora.org/

That certainly doesn't have an officially sanctioned way to program for it. Just a community oriented around it.