KPV hasn't been updated in a year, because the focus moved to KOReader, so there might be some bumps on the road.
https://github.com/koreader/koreader...allation-Guide
And the first post of this thread should cover it.
The latest nighly build *should* ship with a KUAL extension. If it doesn't, grab a koreader Kindle nightly and pilfer the extensions folder from there, the script is completely backwards-compatible (unless I messed up :x).
EDIT: No, don't do that, while the KOReader extensions does handle legacy devices, it's not exactly made for KPV, so it won't work without minor tweaks. (mostly fixing the paths).