They're not 'fired' per se, but as with most staff if you become inactive after x amount of time you usually have your mod status removed. Grue and Salty haven't really been active moderating for quite some time and both their mod payments have been zero for the past two months and grue's even longer than that, so that means they handled zero reports and probably why they were de-modded.
In the Portuguese section, one of the moderators has not been online since March. It's been over 14 months since he last wrote something on the forum. I do not believe we need another moderator since the other one is managing to keep the section spam-free. But when he is unable to access, we have a spam flood.