As you can see here, the original Castlevania wasn't only on the NES, but also on the MSX computer. scrimpeh did on the MSX Castlevania what Phil Côté & Morrison did on the NES Castlevania.
This version is different in some important ways. For instance, you must collect a white key in each stage to advance to the next stage. The chain whip is lost after each boss battle. Some subweapons can be bought from sitting bystanders in white or red clothes.
Note: To play the OMR file, you'll need to use the Panasonic FS-A1WSX bios and openMSX 0.8.0.dev-11840.