Are applications from unregistered developers allowed to run on your Mac?
Did you extract the game with the built-in Archive Utility of macOS, or some other application (like The Unarchiver)?
I extracted the game using the built in Archive Utility. There isn't an option to enable unregistered developers, however, there is an option to allows apps "From App Store and identified developers", which I already have ticked.
To open an app from an unidentified dev, you have to go to Security and Preferences and press allow anyway for the app. I've already done this- but the app still won't open. I've also tried restarting the laptop- no change still.
"On Windows/Linux and Mac, just unzip the package and double click the .exe/.sh file or unzipped application bundle"- SL Install Guide
I clicked on the .sh file, but it opened up a TextEdit window contained what looked to be script related to RenPy.
The SL.exe and SL-32.exe both have decompresser icons- meaning they weren't decompressed. Could it be related to that?
When I try directly launching the app, nothing happens. Any suggestions?
The game is a bundle with the Windows version (the exe files), Linux (the .sh file) and Mac (the SL.app). The only thing I can think of is macOS somehow interfering with the launch of the game. Either because of GateKeeper, quarantining or a general permissions error. Have you right-clicked and choosing "Open" from the context menu instead of double-clicking?