As explained by DICE co-founders Andreas Axelsson and Olof Gustafsson in the YouTube video found after the break (filmed at the DATASTORM 2010 party in early February), Hardcore is currently owned by Sony and Psygnosis, and as such, DICE has been unable to release the game into the public domain (though Axelsson claims to be "working on that"). The game is said to have originally been developed with the Amiga in mind, then brought over to the Mega Drive. Axelsson and Gustafsson reveal that it was "99 percent finished" before being canceled.
Given our love for sidescrolling shooters, we're hoping that Axelsson's intention to release the game publicly eventually pans out. Whaddya say, Sony/Psygnosis? How about you folks get together and work out all this legal mumbo jumbo. For us.