Hi Ken and Roberta Williams,
I have been a Sierra gamer for decades, and, more recently, have became a Commodore 64 retro gamer. I know this may sound strange, but there are quite a few new ports coming out for the nearly thirty six year old computer.
I recently read that Mystery House entered the public domain some time ago. Do you have the source code, so I might try to port it to the C64?
Thank you for your work,
Will Howard