I also don't think much of Mr Cale but what if there are some legal problems that prevent a release? Maybe the agreement with all the people involved was made in a way that they should be given royalties based on sales? Maybe Cale doesn't own the complete rights to the Amiga version of Putty Squad? This would also explain why he didn't sell off the publishing rights of the Amiga Putty Squad back in the 90s... some companies were seriously interested in publishing it and I think he could have made some bucks back then (at least the Amiga market back then was still bigger than it is today).
On another note, somebody mentioned that Jason Page wrote the Amiga music. Did somebody try to approach Page and try to get the music he wrote for Putty Squad? I'd be very interested in this because I've always enjoyed the work of Jason Page.