Is it possible to get rid of the Javascript code?
At drupal.org user Jaypan propsed to implement a new module (named e.g. killjs) which would have to implement hook_js_alter()

&lt;?php
function killjs_js_alter(&amp;$javascript) {
  // Insert code to check whether JS should be killed or not.
  $javascript = array();
}
?&gt;


This, however, would be very laborious for non-experts since it would be necessary to do a more or less complete analysis of the Drupal code base first. User leymannx proposed a solution which may be realized without developing a new module:


Javascript is deactivated only for a specific theme, here called custom_garland.
Copy file modules/system/html.tpl.php into the customized theme folder as /sites/all/themes/custom_garland/html.tpl.php.
In the copied file html.tpl.php delete the line &lt;?php print $scripts; ?&gt;.
Clear the drupal cache.
Select custom_garland as default theme.


Now for guests the page is clean of Javascript! In the backplane, Javascript is still active due to file maintenance-page.tpl.php. This means one can still adust the Garland/Bartik colors or drag blocks.

For me, the maintenance mode works with the above modified theme. Stefan Korn presented a refinement of this apporoach where JavaScript is fully activated for users which are logged in.