It's one of the original smart watches. What really sets it apart from modern ones is the e-ink display and dead simple interface (just a few buttons, no touchscreen). This simplicity means that it continues to do what it does well and doesn't really feel like it has aged badly. Certainly I would rather wear a pebble than a gen 1 Samsung watch or moto360.
It's a delightful bit of kit that was sadly abandoned by owner and it's nice that they are open-sourcing a dead product instead of just leaving it to rot like so many other electronics are.
It was an LCD[0] but you are right that they marketed it as "epaper". But it certainly was not people normally think of as epaper where there are colored capsules that can hold their image without power. The Pebble just had an LCD that looked visually similar to epaper.
It's a delightful bit of kit that was sadly abandoned by owner and it's nice that they are open-sourcing a dead product instead of just leaving it to rot like so many other electronics are.