title_body: Can I use a third party software as a full OS replacement on a Kindle Keyboard?
upvoted_answer: I do not think that there is any measure to stop you. Maybe except for the fear that you end up bricking the device by not being able to connect to it from your PC. 
  
  I do however not see a reason to do this. The only alternative firmware that I know of is Duokan, which works fine in dualboot. So there is no need to remove the original system.
  
  Also since the Kindle is already running a Linux (without an X server though). So you could just install the programs you want without having the trouble of missing drivers etc.
  
  So all in all it should be possible and I do not think anything would stop you. But lacking any alternative options, I do not see why one should do it.