[threeseed]

Safari Developer Preview is stable and available out of sync with the OS.

It does make sense that it is shipped with the OS since Safari is just a wrapper around the OS WebKit library which is used across many apps and services.

[tambourine_man]

Safari Developer Preview requires the latest versions of the OS, so it's not of much use.

The WebKit library should be always stable. In that case, I don't see a problem with other apps relying upon it.