Earlier quoted context omitted.
How would a privacy-preserving payment system (like GNU Taler) obviate the need for Javascript?
RMS and the FSF oppose any proprietary software, and refuse to use it. From a practical point of view, this means having to block javascript by default and at best whitelist it just on sites that are known to use only Free Software on their website. Furthermore, since that browsers and web standards don't provide an automated way to check javascript license before execution, and a site can change what javascript they…
Html and css can also have licenses, and they are frequently generated by server-side code running what is almost certainly a proprietary license, one that is opaque to the user.