snb2txt is a simple Python script to convert Samsung S-Note .snb files to markdown text files. It extracts the embedded images from the .snb and converts the freehand drawings from .zdib format (which ordinary programs can't read) to .png format. I wrote this script for my personal migration from S-Note to using Seafile combined with best-of-breed text editing and drawing apps.
Since this script was an ad-hoc solution for a one-time migration, it is neither perfect nor under active development but I'll be happy to include patches you send me.