Just looked at ALPA's "Guide to Flight Time Limitations and Rest Requirements" booklet. On page 3, the 3rd paragraph starts :
"For example, if a flight crewmember had engaged in commercial flying (e.g., flight instruction, charters, etc.)...
So I would take that as no flight instructing without telling your employer.
As far as the references in the other posts: you guys have the ASA flight library series too, huh?