Why not ask around on homebrew circles?

it will probably be not possible

i've got the 'app' which works locally (streetpass). i wonder if it could eventually work with spotpass. tho i suppose not if the actual program was never designed that way...i don't really know how it works haha

I think a pictochat/flipnote clone mockup would probably be very easy to put together.

Honesty NGL it would be pretty awesome to see a flipnote type homebrew app, where you can create, post and share short animations with additionally NFC and spotpass functionalilty. Could probably host it on github pages too to save money on hosting, storage and domain-name.

use hShop and type in PictoChat.

I guess in a way, one could make a ultra small Bare Metal server that could host pictochat rooms. however, would be a 'use at your own risk' sort of deal.. cause bad actors everywhere sadly :(