<<Disclaimer: Verify this information before applying it to your situation.>>

In response to my question about whether there Is an authoritative,
on-line source of information about these ingrediants, how they are made,
and the likelihood that any of them are, or are not GF, I received the
following information:

The following sites contain information about how they are made, but the
information does not seem to me to be sufficiently detailed to be of much
help to celiacs:

 http://www.maltcompany.com/processextract.html

http://www.prairiemaltltd.com/malting.html

This site (Kellogg's FAQ) indicates that their malt flavoring may be made
from either corn or barley:

http://kellogg.marketlocator.com/kelloggs/us/kelloggsfaq.nsf/
1fc541fb8878dbe9862568f5006b7c2a/82c2f40f0d3f3c058625689d00514f6c?
OpenDocument

A number of posters directed me to celiac.com and its Safe and Forbidden
Lists.  Going there, you can access some articles by Don Kassarda which
contain information that is more specific to celiac.