The game was originally funded on Kickstarter, back in December of 2012, where they secured $15,457 funding. A Linux version wasn't in their original plan, but they were open to supporting it in future.
The game released on Steam a few years ago, with a post on Steam asking for Linux support being around for a while too. Interestingly, the developer said back in May of 2016 that they thought it would be "great" to have it on Linux. Took a while, but now it's released!
About the game:
A Kick-Ass Blast of 16-Bit Sword-and-Sorcery Action!
Steel yourself for a relentless display of might and muscle…of brawn and bravery…of magic and mayhem! Can you cleave your enemies’ skulls, plunder all the booty and flex to impress the barbarienne of your dreams? Inspired by heroic fantasy fiction, Tiny Barbarian DX combines engaging 2D platform action and combo-based hack-and-slash combat with retro-style pixel art and a loincloth-stirring chiptune soundtrack.
Thanks for the tip Xu!