Regarding honoraria received, unless the museum who employs this
    individual paid for that individual's education, I would say
    that any money received belongs to that individual alone.  There
    is not a conflict of interest unless, as you say, the work in
    question was accomplished on staff time or there was a
    pre-arranged agreement stating that the individual would not take
    any paid work outside of the institution.

    I know of numerous curators/museum profesionals who do work on the
    side, often for smaller museums and publications that cannot
    afford to employ a full-time person--me being one of them.
    Anyway, after taxes, it's a pittance!

    John Handley
    San Francisco