It's not legal. They are hoping that people will be chill given the circumstances. Controlled digital lending has to match the model of a library/video rental stores where you borrow/rent something for a few days then return it. Even if you are not actively using the App/Website, which is easily detectable, they cannot return the item to their digital pool while you have it checked out.
Companies have tried to create Just In Time (JIT) media services that return digital items to a pool when you are not actively using them. This essentially creates micro loans with a time span of minutes to hours.
I can't remember the name of the company that was attempting this but they were shutdown due to a copyright lawsuit.
EDIT: They actually mention the company in the FAQ. ReDigi lost their lawsuit [1].
Companies have tried to create Just In Time (JIT) media services that return digital items to a pool when you are not actively using them. This essentially creates micro loans with a time span of minutes to hours.
I can't remember the name of the company that was attempting this but they were shutdown due to a copyright lawsuit.
EDIT: They actually mention the company in the FAQ. ReDigi lost their lawsuit [1].
[1] http://www.ca2.uscourts.gov/decisions/isysquery/68b0f5b0-959...