Not to avoid unfair competition, though. That's just for funding because they're not entirely tax-funded. In this case, the DWD is already tax funded and wants to provide its tax-funded information to the people who paid for it.

That also seems odd

It's a way of funding them as good as any other. Personally I prefer it: I don't watch television so from my point of view the budget of the public TV channels should be as small as possible.

i don't go to the library often because i buy books, but i don't think the library should be ad funded, I'm happy to pay for it in case someone else needs it, their knowledge will benefit me later anyway

i have a similar theory about public TV

That seems like a dishonest comparison. While it's true public television has some divulgation programmes, they are usually pushed to the secondary channels and they aren't watched by many people. If public television consisted only of those programmes, its budget would be much, much lower, and I would be happy to pay for it.

The truth is that public TV nowadays contains lots of series and movies (in many cases, American), cooking programmes, tabloid celebrity stuff, etc that they think they must do to stay competitive with private TV. And that's rubbish.

TV is about as far away from beneficial to an individual or society as you can get without straight up poisoning or stabbing people. The less it is consumed, the better. You're not helping anyone or society by encouraging others to watch it.

I take it you're American?

Do any of these "specific laws" force them to run ads, though?

No. There are anti-competitive laws that prevent the federal institutions to prop up a tax-funded competition to commercial products, unless specifically allowed/mandated by law.

I'm not saying it's the case here, but why not? The law could say they are forced to run X minutes of ads per hour, or that X% of their funding must come from ads.