>do they lend them to you while you pay
Pretty much. You can keep them but the software you use to play them won't allow you to use them unless it knows you have an active subscription. It's actually a really good idea if implemented properly (see eastwest) because shit like this gets expensive very, very fast (see eastwest) and the best libraries (see eastwest) all use proprietary formats and players that are incredibly difficult to crack (see eastwest, it took like 14 years to crack their old player and libraries)