> Daraus ergeben sich auch die zwei wesentlichen Anspruchsvoraussetzungen, die „soziale Förderungswürdigkeit“ und das Vorliegen eines „günstigen Studienerfolges“.
That's from their page, for me this looks like you have to pay it back if you, for example got bad grades, in fact I can ensure you, that the limit is 50%, if you screw up in more than 50% of your courses, you are done.
There is a difference between paying back and continue receiving the stipend.
In general, you need to complete around 50% of your courses to continue receiving the stipend next year, but you only need to pay it back if you drop out in the first year and have completed less than 25% of the courses. (Exact numbers depend on the type of program you attend)
As far as I can remember I had to finish my studies in a certain time frame, I think plus max 1-2 semesters (günstiger Studienerfolg). Not finishing on time would have ended the scholarship. And in terms of "soziale Förderungswürdigkeit" I think a was only allowed to earn a certain amount of money on top of that scholarship. If I had earned too much I think I would have had to pay it back (or parts of out) for the current year. But long time ago, I had an appointment with the "Studienberatung" in Klagenfurt who answered all my questions, fantastic service!