@Servok, I guess you are speaking of my Execute a Script in Terminal plugin.
If you're going to do what @peternlewis has suggested above you have to change the "getvariable"-style syntax (which is KM7 only) in the AppleScript to the old syntax. See here how to do it. But I'm not even sure if the old syntax was already supported in KM5. (?)
If it doesn't work then strip the Variables part of the script or use the script contained in version 1.0.1 of the plugin which should be compatible with KM5 (but it doesn't allow you to use KM variables in the Terminal).