I'm currently writing a application that would benefit extremely from caching, I'd like to use the NSCache class which delivers exactly what I want (in-memory caching with cost, key-value pairs, and automatic cleaning). However, NSCache is only available for iOS 4.0 and greater but I want to target iOS 3.0 too, so I can't use it (not caching on older devices is sadly not an option).
Before I start writing my own cache class, I want to know if there is an existing class that I could use (preferably not under an copy-left license).