Quick Summary: All you need for Calibre to detect and connect with the Kindle Fire 2 is an updated libmtp.so that has the correct vendor/product for this eReader. That’s all you need for Linux, but an updated DLL will do the same on Windows, and I presume the same is true for OS X.
Calibre is great. I’ve used it since I got my first Kindle, many years ago, to backup my eReader, to push Gutenberg library files to it, and to download RSS feeds. It’s been working great and is real easy to use (with a few exceptions).
The other day I decided to buy a Kindle Fire at the discounted price of $129. It’s not the Fire HD, just the regular Fire with the crappy (2012 standard) screen. But I had seen it in a store and really liked it, and I thought I could use it as a development platform for my books.