You said the magic word and summoned me!
It's been a bit of time since I've worked on that, but basically OpenFrameworks assumes that OSC is coming in over UDP, and all the libraries are built around that assumption. ofxOscuino doesn't try and change that—it just sets up a UDP channel and bridges between UDP and SLIP.
This means that it goes ofxOsc->UDP->SLIP->Arduino, and back Arduino->SLIP->UDP->ofxOsc.
This is obviously less efficient than if you rewrote or created a version of ofxOsc that emited SLIP directly, but unless you have really high demands on OSC, you're not going to run into problems, and it's much simpler to use.
(And if you have that level of performance demands, you shouldn't be using OSC over serial, but something more performant!)
