can a defendant be liable for the act of a no-billed co-defendant? Can one aid, direct, encourage and etc someone who has been no-billed?

A no bill is simply a decision by a grand jury that there is, at that moment, insufficient evidence to indict. It is not a formal finding of fact. It is not an acquittal that closes the door forever to prosecution. It is not a declaration of innocence.

Of course- one joins RMN as an "unindicted co-conspirator!" It does seem plain in JB's clear phrasology; a grand jury no-bill works no estoppel, etc.

But, to hold the defendant liable you will presumably have to prove the conduct of the conspirator beyond a reasonable doubt- a proposition not much encouraged by the decision of the grand jury.

Martin, as PG Wodehouse used to make Jeeves say,"You've touched the thing with a needle."