If the union so desires, it could state that no union member may do all the aforementioned jobs at once unless they have at minimum an indelible 5% ownership stake in the company; bear the title of Chief Technical Officer; report only to the CEO, COO, or directly to the board; and have no employee subordinates. It sets the expectations for any company wanting to do that. Any company wishing to ignore it can still hire non-union employees, but the union employees are instructed to embargo any company that does not meet the standards for employment.
Hobby projects are irrelevant. There is no employer. Unions are a cartel for paid labor by employees, where there may be a power imbalance between owners, managers, and laborers. In a hobby project, the worker is always the owner.
FOSS is likely unaffected. Any employer that has FOSS projects is already reined in by the threat of forks. In the extreme case, the union could manage their own forks of FOSS projects, and refuse to merge changes that don't meet union criteria.
It isn't about whether anyone is paid, but about whether everyone is following the cartel rules.
Why would the union rules require separate people for two positions? Why would this be relevant to open source and free software? Why would it be relevant to hobbyists? And so on. I just don't see these problems in other fields. There's unions for actors, and stagehands, and janitors, but I still have a local amateur theatre in my neighborhood, and the lighting director sweeps the floors when that needs doing.
Whenever I say the word "union", all the complaints I hear against them from programmers sound like straw men. That makes me believe that it's the right track.
You refused to understand my post and downvoted to disagree.
Your position is, therefore, refuted by your own dishonesty.
A few ideas, not in any specific order:
It would kill start-ups, wouldn't it? If you have to obey union rules, you can't have one person who's the DBA and the project lead and the primary programmer and and and because those are all different jobs and require different union employees. Great if you're Microsoft and can afford it, but otherwise...
What would it do to Open Source and Free Software? Can it be Union-Certified if it's made by people who aren't all being paid? If a company has to Look For The Union Label, as the song goes, is it going to be allowed to use software which comes from outside the corporate sphere?
Related to the above, what would happen to hobbyist programming? Would it be regulated out of existence entirely, or merely relegated to people writing software nobody's allowed to use because it was made off-the-clock?