> Рассчитывается очень просто: автор рассчитывает на рекламу в качестве оплаты.

Интересно, что в вами же приведенной публикации авторы поднимают тот же вопрос.

The Creative Commons Attribution (CC-BY) license complicates the analysis for courts, as photographers basically make their works available for free to users as long as the secondary user attributes it to them properly, hinting that the licensor’s primary market interest is in attention or credit rather than financial reward. But in the case of the copyleft troll, quite the contrary is the situation; these licensors claim a robust market for their photographs and seek license fees of hundreds or thousands of dollars when the attribution goes awry.