For now, the Itch client allows a way to play the multiple mods/games (e.g. COAS, GOF 1.2, ERAS, etc.) with just one set of Maelstrom.exe + modules/*.dll fileset; the old cd version required a separate copy of the *.exe + *.dll files for each one. However, the Itch install does not let me modify the special Itch manifest file to tailor the file location of each place. So I added instructions to change it, but it is not optimal if someone chooses file locations that are different than the hardcoded, supplied manifest file.
A work in process is to perhaps provide a single executable that will allow just one manifest entry in the Itch file to launch that, and the new executable will allow one to select from a dropdown list the engine version to play (e.g. DX8, DX9 32 bit, or DX9 64 bit) and a dropdown of the various mods/games, but that will take some time to develop.
I just wanted to make it easier to keep current on the engine, by only having one, because multiple copies would require a person to download and copy them all separately, and remember to keep them updated manually, but the Itch client can automatically keep a single one updated for you, and also provide a simpler way to launch the separate mods by just clicking a button in the Itch client. But you are free to break that update process and simply copy the Maelstrom.exe, Config.exe and the modules folder to each mod/game like the old game used to be.