I don't think they provide downloads, but the document includes an offer to obtain the source:
Components of the software used in the vehicle may be free and open source software licensed under the terms of license of the GNU General Public License, Version 2 (GPLv2), GNU Lesser General Public License, Version 2.1 (LGPLv2.1) or GNU Library General Public License, Version 2 (LGPLv2). Upon request, we will supply the source code of the components licensed under the GPLv2, LGPL v2.1 and LGPLv2 on a data-medium (please specify the designation of your vehicle). Please direct your request to the following address within three years after vehicle delivery:
The copyright holders usually do not provide any warranty and assume no liability whatsoever for the free and open source software components. Note that any modificati- on to the vehicle of any kind can void any warranty claim.
