I sort of remember that thread.
Just checked my laptop, for MJPEG CODEC's, and all I have are the Morgan and MainConcept (installed manually), and then the Panny/Lumix and Nikon MJPEG CODEC's, installed with the cameras' drivers, or their included cataloging software. I have QT Pro on the laptop, and not one Apple MJPEG CODEC. However, my QT Pro is a few versions back, at 7.6.9 (do not upgrade that, unless I have issues), so perhaps my version just did not include any MJPEG, and later versions do?
Maybe others can comment on a fresh install of QT Player of the latest version?
Hunt