Honestly...a Mac OS/X "installer"isn't really necessary. Even in the Time Cook era---what one might call the Desktop iPhone era---a Mac is still fairly simple to use (Catalina being the first huge exception going forward).
So, unless you have Catalina, all you really are lacking is experience, and that we certainly have on the board.
All a Mac OS/X Installer usually does for simple Apps like PCGEN is install them into the Applications Folder, which really isn't the best place for PCGen in any of the "Mountain Range" versions. And if the user doesn't already have Java, they will need to download it and install it separately, anyway (new rules).
So...I argue we need a fairly clear, step-by-step installation guide in a plain text format that covers Part A:Versioning PCGen and Java; Part B: PCGen; Part C: Java. Maybe we could cover creating an alias or a "shortcut" that launches PCGen in the background (sudo nohup ./pcgen.sh > pcgen.out 2>&1 &) that one could place on the menu bar.
But a full-fledged installer seems like overkill. Though I was not aware it required a developer's license? I'm not positive that's true, unless y=one wishes to use Apple Developer Tools.