The first line on OnePocket.org says Unless clearly contradicted below, general pocket billiards rules of play and etiquette apply to One Pocket, and complete General Rules are available from the World Pool-Billiard Association (WPA).
Below is from WPA http://www.wpa-pool.com/web/the_regulations#20
20. Cue ball fouls only
If there is no referee presiding over a match, it may be played using cue ball fouls only. That is, touching or moving any ball other than the cue ball would not be a foul unless it changes the outcome of the shot by either touching another ball or having any ball, including the cue ball, going through the area originally occupied by the moved ball. If this does not happen, then the opposing player must be given the option of either leaving the ball where it lies or replacing the ball as near as possible to its original position to the agreement of both players. If a player shoots without giving his opponent the option to replace, it will be a foul resulting in cue ball in hand for the opponent.
This one is good enough for me.
And if something happens that isn't covered by the rules....
..there is the concept of 'common law' and 'common sense'.
I feel anything that affects the RUN of the balls has to be a foul.