The past release of 27.9.15 ArcticFox has the Developer Tools working again, they were broken previously because of excessive work on Private browsing.
You can see them here in full action:
ArcticFox continues the work as a fork of PaleMoon trying to catch up with past releases of FireFox.
It has been succesfully backported up to MacOS 10.6 SnowLeopard, is working reliably on Linux x86, amd64 and PowerPC 32bit and 64bit.
If you like the browser, we need your help!