If you are talking about making a "dry" powder mix that the user will reconstitute - then the Butter Buds would work ... and you can ignore the rest of this. If you making a liquid sauce ... you might want to read on ...
The only problem with using Butter Buds is that after being reconstituted - it has to be refrigerated and only has a refrigerated shelf life of 3 days, according to the Butter Buds FAQ
"Butter Buds has a shelf life of approximately three years when stored under cool and dry conditions. Once Butter Buds Mix is liquefied, it remains fresh in the refrigerator for up to three days. To keep Butter Buds Sprinkles free flowing make sure to close the top tightly and keep in a dry environment."
One viable option might be to use a butter flavored oil since they are already liquid and do not require refrigeration - it should work in any recipe which orignally used butter since butter is fat.
The commercial guys use something that taste and smells just like, or more like, butter than butter ... but I can't remember what it is!
I know I found the information in either Shirley Corriher's Cookwise
or Harold McGee's On Food and Cooking - The Science and Lore of the Kitchen
(Revised Edition). You might check to see if your library has these or can get them on inter-library loan for you if you don't have them. I know I read it in one of them. I would go look this up for you but I'm in the process of getting ready to move in a week or two and I have no idea which boxes my books are packed in - or which stack of boxes in the garage they might be in.
Sorry I couldn't give you a better answer ....