Holger has instigated and maintained several popular python tools, among them
pytest, tox, devpi and the PyPy project. He gave many talks and trainings
at international Python conferences but has reduced his "talk" appearances
in recent years, to care for his child and also because of orienting towards
more "cross-language" communities. Since 2017 he is heavily involved
with the Delta Chat project, a new Chat-Over-Email messenger, available
on Android and in early beta versions on iOS and Desktop platforms.