free distribution
Used for distributing items, software, or materials at no charge, often in official or promotional contexts.
This software is distributed free of charge.
We distributed pamphlets for free at the event venue.
Similar meaning, but 無償配布 emphasizes the absence of compensation or obligation, while 無料配布 simply means 'free of charge'.
Compound of 無償 (free of charge, without compensation) and 配布 (distribution).