README.md: Add a note about the monitor-source

Signed-off-by: Gergely Nagy <algernon@madhouse-project.org>
README.md: Update the legalese

Viktor Tusa contributed a significant amount of code, recognise that by
adding him to the top-level author list.

Signed-off-by: Gergely Nagy <algernon@madhouse-project.org>