Thomas why on earth would a person with sane minds change existing APIs all the time just for fun and to make software developers unhappy? Even open source developers are normal people (to a certain degree

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You cannot say open source is always better, the same is true for closed source. But in a small market where nobody can really make money and investing money is not reallly attractive only open source guarantees existence of a platform. If your product depends on the interest of one person and this person f.e. looses interest the product vanishes. That already happened with lots of amiga software and that can happen to the OS of course too.
It is not relevant if you are happy about the Aros 68k branch, it exists and will continue to exist with Vampire as main hardware target (and UAE).
BTW standards are set by the leader.., that can be the official version but must not. Regarding forking... we are talking about a theoretical danger here. You must find developers with both skills and willingness to invest time in it. A rare requirement. I do not expect much forks "if" AmigaOS would be open source.