They do have their own network because they integrate more than just iMessage. It's "Apple's network" because Apple won't allow anyone else to run a server. Adversarial interoperability might ruffle some feathers, but we wouldn't have Venmo or any financial apps without it.
They advertise Beeper Mini (the iMessage component) separately from Beeper Cloud at the moment. Probably because of the gray area they're operating in. Completely agree with Beeper's approach though. Defaulting iPhones to SMS whenever an Android device is in the chat makes the network less secure for everyone. I would personally prefer being able to use iMessage with my friends that have Android devices so I wouldn't need a couple of different apps with varying degrees of privacy and security.
They advertise Beeper Mini (the iMessage component) separately from Beeper Cloud at the moment. Probably because of the gray area they're operating in. Completely agree with Beeper's approach though. Defaulting iPhones to SMS whenever an Android device is in the chat makes the network less secure for everyone. I would personally prefer being able to use iMessage with my friends that have Android devices so I wouldn't need a couple of different apps with varying degrees of privacy and security.