I have a Kindle and never read nor use any DRM books. You don't need to use Amazon's software or service or anything. You can convert files into .mobi format using open source tools and use a programme like Calibre or just put the files in the "documents" folder of the Kindle to load them.

Using a Kindle without DRM is very possible.

If you turn off wireless, then it will never try to do any software updating.