I have a German translation of the BPNS - though I never used it in any studies. I also have a translation of Sheldon & Hilpert's (2012) Balanced Measure of Psychological Need Scale.
I am facing the same problem right now in my research. Does anyone have the german translation of the general need satisfaction scale by Ryan & Deci? It would be awesome to be able to use it with the German students.
Seems there is growing interest in this issue, so I'm stepping in again:
I do not have a validated version of a German BPNS, but we have recently validated a German translation of Sheldon & Hilpert's (2012) Balanced Measure of Psychological Need Scale (BMPN) - we found evidence for its validity on both the between-person and the within-person level; see these two publications:
On a side note: we chose the BMPN instead of the BPNS since the latter scale showed suboptimal factorial validity in work by Johnston & Finney (2010; see here: https://eric.ed.gov/?id=EJ897006)