I'm surprised no one has noted the copyright is to Design Science - this is a small company in my hometown who are still around. I've spoken with their CEO a few times and I wouldn't be at all surprised if the source code was lost, or somehow at least wasn't being made available to Microsoft (I doubt it ever was). It's a really old school shop who seems to have largely been coasting on the licensing of this one component for the past couple decades and I wouldn't at all be shocked to find they no longer are capable of maintaining it themselves.
I noted it - thanks for the background info on the company! I also assume that either they are not able to maintain the software themselves, or they have lost the source code, but it might also be that setting up the toolchain to compile such an old piece of software is more effort than just patching the binary.
This is such an underappreciated aspect of code stewardship. There are powerful tools for source control and archiving. But ensuring that state of code could actually be built at an arbitrary date in the future is so much less assured.
I would guess the build environment involves lots of dependencies, lots of special config, lots of stuff which has to be the exact correct version, and all that knowledge has been lost as people have left the team and it wasn't properly documented.
Sure, you could spend a couple of weeks setting up a suitable environment again and relearning everything from scratch, but binary patching is probably easier.
According to an Ars comment: "I've got an older version of Mac Office (2011 I think), and there's a version of Equation Editor in there with a 1990-2010 design science copyright on it, so they have some version of newer code they could swap the old office one for."
