A topic from AEG's L5R CCG Rules forum, copied for Oracle of the Void from a copy of the forum saved in October 2015, so pages it didn't save are missing. Players' names are left out; the rules officials are named. Rulings are as they stood on these dates; later rulings, the rulebooks and the Rules Archive may differ.
A player, 20 July 2012
Costs and Restrictions, Gold Production: It is permitted to overpay a Gold cost by any amount, including producing Gold to overpay a Gold cost of zero on (for example) a Strategy card. It is not permitted to pay Gold to bring into play a card with no Gold cost stat (such as a Ring or Region), or for an action with no Gold cost on a non-Strategy card (such as a Personality or Follower).
Serenity of Air: Limited: Put this card into play. Discard all your other Kata in play. Battle/Open: If this card is in play, target your Personality and, if this is the Action Phase, discard a card: Straighten him.
The printed gold cost on this card is 0. I know when I initially play this card I may overpay, but what about using the B/O ability? May I overpay for that action, even though the action is already in play and is not entering play (therefore the "entering play" cost, if such a thing exists, has already been paid).
Thanks.
Jon Palmer (rules official), 22 July 2012
Costs and Restrictions, Gold Production: It is permitted to overpay a Gold cost by any amount, including producing Gold to overpay a Gold cost of zero on (for example) a Strategy card. It is not permitted to pay Gold to bring into play a card with no Gold cost stat (such as a Ring or Region), or for an action with no Gold cost on a non-Strategy card (such as a Personality or Follower).
Serenity of Air: Limited: Put this card into play. Discard all your other Kata in play. Battle/Open: If this card is in play, target your Personality and, if this is the Action Phase, discard a card: Straighten him.
The printed gold cost on this card is 0. I know when I initially play this card I may overpay, but what about using the B/O ability? May I overpay for that action, even though the action is already in play and is not entering play (therefore the "entering play" cost, if such a thing exists, has already been paid).
Thanks.
Per the CR on strategies, the gold cost is paid whenever the ability is used. Therefore there is a 0GC cost for using the ability on an in-play kata, and it may be overpaid as normal.