Royalty-free licensing
A licence that charges nothing per unit sold or per use — which is not the same as free of cost or free of conditions.
A patent or copyright holder licensing royalty-free takes no running payment per copy, device or stream. For standards the distinction matters enormously: since its 2004 patent policy, W3C has required members to commit to royalty-free licences for any patent a web standard needs, while many telecom and video standards rely on FRAND, where the fee merely has to be "reasonable".
The Alliance for Open Media was formed in 2015 precisely because H.265 had ended up with three competing patent pools and nobody could say what it would cost. The answer was AV1. Royalty-free rarely means unconditional, though — defensive clauses that revoke your licence if you sue are standard. And in stock photography, "royalty free" just means you pay once.