Revert "Update License."

Never change the license of a project when not all authors have agreed on that! If you do
such a important change do a PR for it so we can discuss it there.

This reverts commit ffce7f5485679c071bbc6cb20bf0e8ed525221d6.
Switch back to version 0.5.0

Signed-off-by: Simon Busch <morphis@gravedo.de>