how does one save, without income?
Income isn't something handed to people by fiat. Income is something people get by working. And even in poor countries there are some jobs that you can do which don't require capital.
So you could work even harder than you otherwise would have to, and live even more frugally than you otherwise would have to, and save the difference as bitcoins. Providing for a better future.
I'm not saying it's easy. Just that it's desirable, and for many people is possible.
but it is also possible to earn more - and save more thereby - with one's own business; and the higher income implied by that.
and i don't make any money from somebody in the third world gluing sneakers together for nike. i do if they owe me interest... and are capable of paying it.