User:Kate/membership opt-out

Membership of the Wikimedia Foundation:
 * should be possible but optional for editors;
 * should require explicit opt-in by a user

Therefore:
 * there should be a preference or other option to indicate membership or lack there of easily, both for those who want to join and those who don't;
 * opting-in should require an explicit action on the part of the user (joining by default is not acceptable)

The ideal implementation of this is:
 * there is an option on the account creation page explaining that one can join the foundation, with a link to a description of what that means;
 * this box should be unchecked by default, so that indication of a wish to join can be ensured.