ralfkrause Are you sure that the additional files must stay in the lib folder?
These files have nothing to do with the plugin distribution and could be used by another plugin (and this could be useful if the GeoGebra question type plugin would enable to work offline too). That's the reason why I put them there, with other Moodle external libraries to keep things tidy. I've done this already for the MathJax filter.
Anyway, any location would work, provided it is in Moodle path.