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, 14 July 2014
Its text reads: [bow]: When paying for a non-Unique Samurai, he enters play for 0 Gold.
Please can you confirm that the phrase "for 0 Gold." is a variable reduction of a gold cost (and so is similar to Deep Harbour's fixed reduction), as opposed to some sort of substitution or replacement effect. The comprehensive rules list for 'for' seems to apply to a different use of the word as I assume that the entering-play effect of recruiting the card is not somehow contingent on the card being recruited for 0 gold.
Ben Higgins (rules official), 14 July 2014
Its text reads: [bow]: When paying for a non-Unique Samurai, he enters play for 0 Gold.
Please can you confirm that the phrase "for 0 Gold." is a variable reduction of a gold cost (and so is similar to Deep Harbour's fixed reduction), as opposed to some sort of substitution or replacement effect. The comprehensive rules list for 'for' seems to apply to a different use of the word as I assume that the entering-play effect of recruiting the card is not somehow contingent on the card being recruited for 0 gold.
"Enters play for 0 Gold" is indeed a reduction; the same way an effect like "Ryushi has 0F while unopposed," or "You may Recruit a Personality for 2 less Gold," would be a reduction.
An example of a substitution of a cost would be, "You may bow your Stronghold instead of paying this Invest cost."