Weird, that fixed it. I assumed that since the URL was exactly the same whether I ran it with ./nodebb start or ./nodebb dev, it couldn't be related to cache. I suppose I just don't know enough about how caches work.
I installed v0.6.x-dev which may have been the cause. Also, I may not have ran "npm install -g forever" in the nodebb directory. I'm not sure if this would make a difference?
Forever is working fine with v0.5.4 and installation using "npm install -g forever" in the nodebb directory.
I execute Forever using this cron job.
@reboot cd /home/nodebb && forever start app.js