If the script you'd like to call it from is in Script-Fu, then you should be able to just call it normally (i.e. (script-fu-blur-random-map
'(255 255 255) '(195 87 44) '(44 135 195))). I'm not sure what else you would write a GIMP script in, but I'd bet you can call it one way or another.
I'm not quite sure what you mean by the edging question. I'm a GIMP novice myself, so if its a technical question about GIMP I doubt I'll be of much help 
.