Both mugen and the forgotten Fighting Maker are not open source,but IKEMEN is trying to make a opensource fighting game engine.1- It's not impossible!! However, our team grew up a quite a bit after sending the first prototype pets to our testers, and after some debate everyone ended agreeing that we should shift focus to preserving rare programmings (the new members of our team have many rare virtual pets, and I already started giving materials of the rare Hitorikko Angel) or remaking bad ones (like rikourikou-smarty time) and make them avaliable to public, with hight priority to the ones we already started, before starting to develop custom virtualpets like our Tamanoroi. If i had known this before i would have left our little creepypasta to grow, since my raise of hype ended killing it prematurely. I'm really sorry for that.
2- yep, the hanahanami is our top priority to be preserved, and we already have some people that started to gather materials of that, but to make the pet possible, we need to develop and program a system that makes all those features (light sensor, a better sound system) possible, so it will take a time before something be announced.
3- we cannot develop a Magical witches pet without help, someone need to make a full catalogue constipating all features of the pet, as well as all sprites and events. seems that there's people interested in keeping their prices in the skies for some reason... :-/
4- our pets will have opensource code, and free libraries so everyone will be able to access and modify, or make their own programming. but to make possible what you suggested, we should shift our vision of developing virtual pets (almost from scratch) and create a pet engine containing tools and resources that would be intuitive and easy to understand, and also develop a different hardware that must recognize the engine without any possibility of bricking the entire thing in case of errors of the editor. Something how MUGEN and 2DKAKUTOU are to fighting games, for example. it would consume a mad amount of time and energy.
Sorry for having bombed this wonderful creepypasta with my project, was not my intention to take all attention to me.