Sure you can! Hyperboria is built on CJDNS and often their terms are used interchangeably.
CJDNS/Hyperboria are built with the idea that peering with people you know and trust over a direct connection will build out a mesh network.
However, this isn't currently practical for many, but since the mesh can be run over almost any network connection, it can also be run on the regular internet. There are people who run servers big enough for public access, and you can find lists (by continent, country, etc) here: https://github.com/hyperboria/peers
All this and more is explained in the README here: https://github.com/cjdelisle/cjdns/blob/master/README.md
Best of luck!
FWIW, most 5v FTDI cables can accept 3v input, and most 3v routers can tolarate 5v input. I was able to unbrick one ASUS router in a pinch by pulling the AVR chip out of an arduino.
The "correct'" way to build for openwrt is unfortunately very out-of-date.
If you want to try compiling it to install manually, first make sure you can build cjdns. Then you'll need to install the mips crosscompile toolchain, which varies depending on distro. Then you just export CROSS_COMPILE=mips-linux-gnu- and run cross-do to build cjdroute.
If you're on debian I can give you detailed instructions on how to install the mips crosscompile toolchain, or if you want I can just send you a binary.
EDIT: Actually, the new nodejs build system seems to have completely broken mips support, so you're stuck with stable-0.5.