Is it permissible to download paid lessons available for free on the Internet?

There is no harm in benefiting from free lessons, unless it is highly probable that the one who provided them infringed upon the rights of another, because the default assumption is innocence. If the infringement becomes clear, then it is not permissible to take from the usurper, and the one who takes becomes like him, as 'Alish stated in his Fatwas: "A matter concerning dealing with those who possess unlawful [property]... that the unlawful [property] be present in its essence with the usurper... then it is not permissible to purchase it from him... And whoever does any of that, he is like the usurper." It should be noted that some scholars see no harm in personal benefit from copied programs without seeking profit or trading.