Relationship between Goddess Mansion / Leonard / Block Terminator?

So doing a few small updates I noticed that "Goddess Mansion" has in the picture of the manual a mention of "Omega system Leonard", so in trying to understand what the link may be (perhaps they used it to draw some of the pictures?), I looking in turn to Leonard, I noticed the product code and did a search for the first four letters, and found a perfect match with "Block Terminator".
MXDK-12003 Leonard
MXDK-12004 Block Terminator

So my guess is that they were published by the same publisher. But I cannot find anything other than the product code to link them. Does anyone else have any idea?