Working on my "UX and Open Source" talk, it's clear the challenges are much the same as with proprietary software: you either understand what UX has to offer or not. The key difference is philosophical.
Some FOSS teams feel central control is unnecessary. As UX is often about making hard tradeoffs, it feels counter to the culture.
However, FOSS teams need to make hard technical decisions all the time: they DO have (some) central control! UX is no different