This is interesting, i initially just glossed over it but looking closer it is basically line bonding to one of their servers.
With separate connections you have multiple options.
1: Use them separately. (you connect to one at a time.) This gives you a backup connection if one goes down but doesn't use both connections at the same time.
2: Load Balance. (I bought one of these
http://listado.merca...com.ar/Tl-r470t but you could just as easily use an old pc with linux to do it.) This is basically set-up to split connections over both lines so that if 1 person is maxing out one line watching youtube or something the router will route other traffic through the other line.
3: Bonding through VPN. This is what that kickstarter does in hardware, i presume they limit the connection so it can only connect to their VPN. If anyone with 2 network cards fancies it all you need to do is setup a VPS to bond the connections for you and instant fat pipe!
The TL-R470T+ can connect via L2TP so it may be possible to use it too, i'll be giving it a wee go later at some point.
http://www.zeroshell.org/ is a nice ready made Linux OS, if you can find a company setting up VPS's with it.
you can watch someone doing it on youtube here
Added bonus is that if you get a VPS in the UK you can stream BBC or a US VPS and you can stream the US ones.