Frankl’s use is faithful and openly sourced. In Ärztliche Seelsorge the German runs “…leuchten soll, muß dulden, daß es brennt’, sagt WILDGANS und meint damit wohl: daß es leidet” — says Wildgans, and by that he probably means: that it suffers. The Winstons rendered the same passage in English as “‘What is to give light must endure burning,’ Wildgans says. That is, it must suffer.” Frankl was pressing the poet’s image into service for logotherapy’s claim that suffering can be an achievement rather than a defeat.
The failure mode is ordinary and mechanical. A reader meets a memorable eight-word sentence inside a famous book, copies the sentence, and cites the book’s author. Denise Levertov did the honest version of this in 1975, using the line as an epigraph and citing “Viktor Frankl, The Doctor and the Soul” — accurate about where she found it, silent about the fact that Frankl was quoting. Strip the book title on the next copy and you are left with a bare Frankl credit, which is what Goodreads, the quote aggregators and a thousand social posts now carry.
Worth noting for anyone checking: the line is not in Man’s Search for Meaning, the Frankl book it is most often mentioned alongside. A full text of that book contains neither the sentence nor Wildgans’s name.