Just to fairly represent the contention, their extended argument seems to differentiate "third party questions" into one of two categories:
- Getting things to run on Ubuntu, and
- Problems with those things
The first would be on-topic and the last would have to go elsewhere.
##I disagree with that
Ubuntu is a distribution and configuration of thousands of packages. Almost everything is third party by some definition.
You might argue that some applications are more "core" than others. Firefox is the default browser on most Ubuntu desktop variants, so if you're going to make that argument, why would we support Firefox less than we support Unity or LightDM or PulseAudio?
More than anything, it seems like an excuse to not help somebody. Our raison d'être at Ask Ubuntu is to help Ubuntu users. Our scope frays and blurs with other sites in some areas but I'd rather over-encompass something than trying to pigeon hole every question perfectly.
Otherwise we might all as well back up and move to Super User.