There is no official policy. No one has gotten together and said, "this is what we agree on." There isn't even an implicit agreement, because from what I can tell, what people believe on the matter (or practice, anyway) varies widely.
As for me:
Participating in multiple board RPs--I try not to anymore, but I have before, and it's worked out in the end. Up to, firstly, the GMs, then you.
Participating in chat RPs as well as a board RP--I have no problem with this. I don't see time as an issue, usually--board RPs can take months to well over a year for a handful of days of in-character time. Thus, in about a week's time or so, the chat RPs are already well ahead of the happenings of most board RPs. Even considering longer board campaigns, chat RP time is damn flexible, and not really measured or tracked closely in most cases. Also, CIRP happenings and such are often similarly flexible and unlogged, to an extent. Staying out of GMed chat RPs is probably a good idea, however.
The only issue I consider is character development. As for that--I have not yet been unable to smooth anything of this sort over. Using my more established characters generally makes this easier than using new characters, who are (for me, at least) more apt to numerous and/or dramatic changes. <p>
<center><small>"We are just poor, wandering corn farmers..."
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