I've mentioned here a few times about online versions I've been working on.
In addition to the main MST GitHub (
https://github.com/celstark/MST), I've got one for the online work (
https://github.com/celstark/MSTonline). Now, much of that is a bit behind my current code, but I've just posted a JATOS + jsPsych experiment (bundled as a .jzip for easy import into your own JATOS) that has a current, functional experiment. I also updated the commenting to get it so that someone else might have a chance to understand how to use it and modify things to suit their needs.