Developer of a tool says I need to run an exe file and chmod it on mac
I have downloaded the program and can confirm that the exe file is indeed an ordinary exe file - and definitely not a script file for Linux or anything of the sorts.
I would assume that when the author mentions that the project is cross-platform, and allows running on Linux and macOS - he means that you could install the Mono Project and run the program that way.
However executing the exe file via mono like this:
mono dxDD2RenPy.exe

doesn't actually work. It does work with other .NET cross-platform exe files though.