It depends on specific device and its architecture.
Those that are built on top of Android, typically tend to get AOSP ports, e.g. Nook (here's Simple Touch instructions), or Kindles - the latter even has CyanogenMod ROM.
Sony PRST 1 was hacked to expose full underlying rooted Android but I'm not sure if AOSP based ROM is available for it - this might be ...
It'd theoretically possible, but no device manufacturer (except for Amazon) bothered to develop and release emulators.
If you want to make sure that your epubs look OK on each device, you might want to check them with the desktop versions of Adobe Digital Editions, because all major eInk manufactures, except for Amazon, ship with an app that uses the same ...
If you sync via WiFi you should get version 5.2 build 1894. You can check if you have that version via the Settings → About ... menu.
The manual download page might be out of date with the actual version of CybUpdate.bin you download from there, or the download itself might be the 1780.
I have never tried to install that 1780 version as my Bookeen ...
Yes, they do!
In fact at this page you can find the update for your kindle (if it's not a kindle touch, then it's called kindle 5th generation), with the following information (bold is supplied):
We have a new, free software update available for your Kindle (5th Generation). This update automatically downloads and installs on your Kindle when connected ...
After lots of complaints the dots were brought back in the latest 5.8.1 firmware update for PW2 and PW3 Kindles, which you might need to manually download from the Amazon website.
(You can only downgrade to a previous version, if your Kindle had the latest jailbreak installed.)
KOReader is an ereading software available for several devices and platforms. Quoted from Mobileread wiki:
KOReader is a document viewer for Linux based E Ink devices. Currently
there are versions for Kindle, Kobo, PocketBook, and Android devices.
The installation procedure depends on the device. Support forums are available on Mobileread.