How about putting the person on an advisory committee rather than the
Board?  An advisory committee mainly acts as "experts" that you go to
with technical questions, that are not so concerned with day-to-day,
staying-in-the-black, satisfying-the-moneyed-ones as the board is.  That
is certainly not as much of a conflict of interest as being on the board
would be.  If you don't have such a committee, you can start one.

Julia Moore
Indianapolis Art Center