You do not need to sign up to access the library, it is free to browse and use.
There are three key cost types for the apps:
Entirely Free – the app has no costs associated with it, either up front or once you download it.
In App Purchases – the app is completely free to download and offers the option for individuals to make purchases within the app once downloaded. For example, this could be for a subscription to a weight loss programme or to unlock additional content such as exercise videos.
Paid – the app requires payment up front to download. The price is usually displayed under the ‘Pricing’ section when viewing the app information.