The part that's wild to me is that Beeper is collecting revenue from their users for this.

Apple doesn't charge for iMessage, and instead that service is funded by device purchases. Beeper is charging people who haven't purchased devices to help them parasitize the infrastructure of the service, and instead of contributing to Apple's operational expenses, they're pocketing the money.

There's no scenario where this stands, even if iMessage came to non-Apple devices Apple is probably going to charge users if they're not buying Apple devices (I can't imagine it being an ad-driven service).