How much revenue are you thinking there is in converting archive files from Stuffit versions 4 and 5 (released 1995-1997) to Stuffit version 3.5 (originally released 1994). As far as I know, neither has been commonly used since the release of MacOS X in 2001 (I mean, older Mac OS machines were surely being used for several years after that too, but it's been a while). It does not seem like a particularly likely revenue opportunity. Like most other archaic orphaned file formats, with a few exceptions.

I'm not totally sure who the audience is for this hobby project even! It says people running Mac OS System 6, which was released in 1988, replaced by System 7 in 1991. (If you were running System 7,or system 8 released in 97, or system 9 released in 99 -- you wouldn't need this converter). I do wonder who these people are running a 1988 Mac OS release, on what hardware, and what they are doing!

A Mac OS System 6 machine CAN connect to the internet, but barely, I think this may have been the first version that did TCP/IP built into the OS, but it was finnicky. It got a lot more solid in System 7.