No, that shouldn't be necessary. Python 2 and 3 can usually coexist. What's your operating system?
I haven't worked on moonshiner for close to a decade, so I was quite surprised to see that it still works fine when I tried it right now 😀 There's just one caveat: You have to run it with Python 2. PyGTK isn't available with Python3 (apparently there's a successor called PyGObject; I don't know how easy it would be to port it over).