Does Weaponmaster allow free gear equips only when played or anytime?

Weaponmaster allows you to equip gear at a reduced cost only when the unit with the Weaponmaster keyword is played.

According to Rule 747.1.b and the related FAQs:

• Weaponmaster is a Play Effect: It triggers specifically when you play the unit.
• Timing: The cost reduction applies only during the resolution of that specific "on-play" trigger. It does not grant you the ability to equip gear for free (or at a discount) at any other time.
• Standard Equip Rules: Outside of this specific "on-play" trigger, you must follow the standard rules for the Equip keyword (Rule 744), which requires you to pay the full cost and can only be done during your own turn, outside of a showdown, and with nothing on the chain.

In summary, Weaponmaster is a one-time, "on-play" opportunity to attach equipment at a discount; it does not change the timing or cost rules for equipping gear at any other point in the game.