Case in point:
* Let's start with the most obvious, because it's a good one: you don't even need to downgrade a PW1 to JB it, the EOL FW is likely to be vulnerable to
BD's JB.
* You don't need to roam the internet to get an old production FW release: just go to the Amazon Kindle Software Update Page for your device, get the link of the latest FW, tweak the version in the link: voilą!
* Every time you see someone bundling content they've not created, run like the wind: it's at best utterly outdated, at worst might do unspeakable things to you or your system.
I'll assume it's simply outdated here, which is still highly problematic, as the bridge has since seen numerous updates to deal with later FWs properly, or even just current annex content.