Hello,
Please try the following to run gpsd without systemd:
FROM balenalib/raspberrypi3-debian:stretch
ENV DBUS_SYSTEM_BUS_ADDRESS=unix:path=/host/run/dbus/system_bus_socket
ENV UDEV=true
RUN apt-get update && apt-get install gpsd gpsd-clients python-gps
CMD gpsd /dev/ttyACM0 -F /var/run/gpsd.sock