Recently, samurai_jazz has been approved for publication on Desura (https://www.indiedb.com) and will be seeing it's full release in the very near future. While I can't pin-point a specific date at this point, it will be within the coming weeks.
The full version will be available for $2.99 (USD) and includes the full adventure not seen in the demo, along with the option for both an easy and hard mode on top of the game's normal mode.
If you would like to see samurai_jazz released on Steam, please vote for it on my Greenlight page for the game here:
Steamcommunity.com