Another typo, in Q's German text v. 2 l. 3: Gem252;te should probably read "Gemüte", i.e. "Gemüte".

The attribution to Henry Suso (Heinrich Seuss) appears to be based on the fact that he mentions the song in a work dated 1328; however, he mentions it as an existing song, not one of his own composing, so the date of its origin may well be much earlier. (It's like we don't say Shakespeare wrote Greensleeves, but we know it existed then because he mentioned it.)

I'm guessing the Peter von Dresden attribution relates to the monolingual German text, while Suso's reference may have been to the macaronic text we know or to a monolingual Latin text such as that I posted above (he only cites it by incipit, "In dulci jubilo &c.", which is inherently ambiguous in this case).

Haruo