> Bestie has a Tin Can? Free calling to other Tin Cans is included for every device, no subscription required.

> Subject to a valid account & our terms of service.

Yeah, subscription aside (though that alone is a deal-breaker for me) I don't like it requiring an account.

Might there be a way that an open-software/hardware device could simply have a person enter, what, a friend's IP address to make a call? Or is there more middleware required to connect the two VoIP?

> Or is there more middleware required to connect the two VoIP?

You need an address of record to translate 111222333 to an actual deliverable location, like a PBX. You can do without it in a software solution, but in the age of NAT having a TURN server is highly advised.

> I don't like it requiring an account.

Remember the value proposition here is for kids calling trusted contacts. You could absolutely and easily build your own VoIP network with Asterisk etc.

Making real phone calls costs real money.

The covers the cost of calling actual phone numbers, which probably does cost the company something.

The direct calls are free, and don't have a fee, because those go over the internet.

Companies like making money.