Non-rivalrous means that a good can be used by multiple people at the same time without reducing the amount available to others. By nature, digital licenses are non-rivalrous.

This means it can be used by multiple people at the same time without diminishing their quality or quantity. For example, a fireworks display is non-rivalrous because everyone can enjoy it without affecting the quality of the show. Likewise, software can be enjoyed by everyone without affecting the quality of the life of the producer or its content and there is no indication that piracy can limit the latter and former.