"It's apparently telling me to "unlink" the butler.exe file. I have no idea what that means or how would I do that, and even if I did, it's apparently locked behind some sort of permission thingy that doesn't even let me open the exe."
This isn't an instruction to you, the user - it's a debug message from the installer attempting to explain what went wrong so the developer can fix the issue. With some googling we can see that in this case, EPERM is an error code indicating that the application failed due to insufficient privileges to perform some operation. Looking further, the debug message says that the operation in question is unlinking a file. The details of that are not super relevant to you, so I'll leave that out.
It's possible the issue is with the installer itself failing to acquire permissions or something, but you can always try running it as administrator and see if that helps.