My understanding of it is (although I'm not remotely an expert on cell culture) that stem cells can in general be made to divide in culture "indefinitely"; the

My understanding of it is (although I'm not remotely an expert on cell culture) that stem cells can in general be made to divide in culture "indefinitely"; the Hayflick limit applies only to (non-stem) somatic cells. Stem cells use telomerase to maintain their telomeres, similar to how germ cells use telomerase to reset themselves to a "newborn" state. Stem cells can progress from "universal progenitors," the stuff of the featureless blastocyst, to embryonic stem cells of various forms, to adult cells (both stem and somatic); this process has to do with changes in gene activation and cell morphology, not with telomeres. When the article notes that these cells can be "multiplied indefinitely," the point is that researchers can prevent them from differentiating into more-mature forms of cell when they divide.