One other possibility is to boot the Mac to Single User Mode and use the Directory Services Command Line tool to join your non-admin account to the administrator group. Well I haven’t found a way to get this work in Mac OS X Yosemite so I’m going to assume it doesn’t work anymore. There was on old hack that worked on older versions of Mac OS X that let you modify a string in ist which effectively disabled authentication.
If that fails, you could try Control clicking the app and choosing Open Package Details to see if you can modify the ist file or whatevever.
