I am happy to announce that Superstar Hero will be released on Steam on June 13th. Here is the store page: https://store.steampowered.com/app/1089080/Superstar_Hero/
In addition to that, thanks to the EasyRPG Player, the Steam version of the game will be Mac and Linux compatible. It will be possible to play the game as standalone (without Steam), but it won't automatically update and setting that version up to run on Mac/Linux might be an hassle.
I wrote a script to easily build a standalone app for Mac, and for Linux, pretty sure easyrpg-player is in your favourite package manager, so no problem here.