The brothers do have some money, I suppose, from their company.
However, I'm not sure if they are using the data gathered from this service, thus resulting in revenue somehow (maybe in their social network).
Replacing SMS I can see, since whatsApp/GroupMe/iMessages/whatsoever is already doing so, but replacing e-mail? Why would it replace e-mail in your opinion? I think IM/chats have a completely different purpose compared to e-mail, which unfortunately is often times used wrongly imho.
The brothers do have some money, I suppose, from their company. However, I'm not sure if they are using the data gathered from this service, thus resulting in revenue somehow (maybe in their social network).