This page collects various versions of WhatsOpen.app
Initially, this page offered just an updated version of WhatsOpen.app v2.1, by Franklin Marmon, released around 2008. That version was 32 bit only and did not work on macOS 10.15 and later. So I re-created a 64 bit app from it.
Later, I got hold of version 2.7 and 3.0, both of which should run on 10.15 and later as well.
See here for a few sites explaining what this app is meant for:
Note that the re-created version 4 is based on version 2.1, i.e. it's missing some of the later improvements such as the Eject, Pause and Superuser commands.
Current re-created version: 4.0.1, requires Mac OS X 10.10 or later (Release Notes)
The source code (Xcode) can be downloaded at github
These older versions offer more features because the source I built version 4 from was not the latest, unfortunately.
Thanks to the original author, Franklin Marmon, for giving me permission to re-release the application here.