Volkswagen (Porsche's parent company) certainly has the scale to make this happen. Seems like its entirely a corporate culture issue, same as what plagues Volkswagen's EVs and newer cars with terrible infotainment systems.
Yeah, but VW and Porsche are into selling cars not OSS so their priorities are aligned with that.
Think of it from the bean-counter's perspective, which run these companies: why would they invest resources into sharing your SW as OSS if that's not gonna sell more cars?
Toyota had the unintended acceleration lawsuit during which an external audit discovered several bugs and deficiencies with their SW, testing, and dev process.
Knowing this, why would any car manufacturer air their dirty laundry in public for the sake of OSS? Their lawyers would definitely advise them to never OSS anything internal out of the kindness of their hearts as that could backfire spectacularly.
This sounds like a good reason to have a little government regulation to align incentives with safety interests.
Welcome to the real world of corporate profit making. You must be new here.
If only because there might be a significant number of findings about accidents that turned out to have been caused by a malfunctioning vehicle after all when right now these are attributed to the driver.
In a way, the German OEMs have been trying to do so, but mostly via different standardization efforts (OpenSCENARIO for example) so that they can easily change suppliers.