The financial transactions done in the IH8MUD store have always been handled externally via https....transactions have been the major push for the https security in the past.
However, that is changing, and Google (surprise) is pushing for ALL sites that manage data (usernames/passwords, etc) to be https by 2017.
It is likely coming...i've been researching for more than a year as other sites have made the transition from http to https...and in some cases, back to http due to issues. I'm waiting at this point, but am seeing more and more successful transitions with clear paths. When MUD can make that transition with minimal chance of problems, it will happen.
I'm surprised that a "warning" is being issues in browsers. I assume ALL username/password sites you are accessing are noting the same warning?