It looks like this doesn't work with folders... or have some kind of hash to detect alteration. While I appreciate you sharing the project, this is probably premature at this point.

Here are somethings that I would consider adding:

    * a README  (update: done! :) )
    * consider making this work with virtualenv by default. This way you can install
      Flask as a library without making me install it for the system. Adding a short
      bash wrapper script really helps here.
    * support for folders
    * sha1 hashes to ensure your files are consistent
    * de-duplication of chunks would be a good thing to add too
    * The way you are sending data now looks like you are using GETs for everything. 
      If you are really going to make this work, you should use GETs for downloading and PUTs or POSTs for uploading.