Research has actually indicated that the link between financial incentives and motivation to work is actually very small: https://hbr.org/2013/04/does-money-really-affect-motiv

Thus widespread availability of "labor of love" open source software, and the relative crappiness of a lot of commercial software.

Money has a huge affect, up to the point that your needs are met. Yes, if your needs are met, and you have time to pursue things you enjoy, you do that, but first, your needs must be met.

If I didn't require an income to cover a family of five, I would be retired, and doing whatever it is that I love at any moment. But instead, I work for a living, for money, to meet our needs.

Most OSS is funded by corporate and wouldn't exist without it

Corporations do provide funds for some larger projects, that is however not anywhere near "most".

Financial incentives redirect labour from useful to profitable activities.

You mean labor is directed towards actions that produce more value than simply the labor put into them. Odd, its like you think that's a bad thing.

Since much of monetary value is related to scarcity, labor is directed to reduce scarcity, not to actions that produce social value.

The pool of people who are capable of collecting garbage is non-scarce, so the price for labor is relatively small compared to the social value it produces.

Advertising is so well rewarded because the attention of consumers is a very scarce resource, so companies put massive amounts of money into capturing some of that.

That statement only holds if you only define "value" as financial gain. I would consider that a dangerous simplification.

That is literally the opposite of what I wrote.

I think this comes down to whether you agree that money == value, and that value == utility (i.e. that people will pay for things that they find useful)

...and, since many (not all) profitable activities turn out to be useful, financial incentives still end up incentivizing useful activities. For instance: [IDE company] employees are incentivized to develop [IDE], I buy [IDE], [company] makes a profit, and the value that I get out of [IDE] means that their activities were useful. Good stuff.

Sure. But others are entirely useless or even harmful. If you want people to implement dark patterns, tracking, advertising, or walled gardens, you have to pay them.

you cannot possibly be postulating that profitable activities can never be considered useful, are you?

I do not see OP stating that "useful" and "profitable" are mutually exclusive. I think it is widely understood that there is "usefulness" that is not satisfied by profit driven organisations, that is why we have non-profits and public institutions.

Call me cynical, but most non-profits seem to be more interested in paying salaries and fundraising than in the actual thing they're supposed to be "about".

And public institutions may serve a useful function, but again seem to be mostly about civil service powerbroking and providing extremely safe employment.

Fine, I'll call you cynical... ;P

There are certainly (often larger) nonprofits with a tendency of overpaying their leadership and/or pushing policies favored by their corporate funders. I would in this context however not conflate "most visible" (ie largest advertising budgets) with "most". Most nonprofits I have worked with are ran and operated by hardworking people on minimal budgets.

Note that he didn't say overpaying, just paying. It is true that in all organisations (including those associations), as time passes, professionalisation progresses, headcount raises, administrative and secondary tasks develop; and self-preservation, self-replication become a goal of its own. There is a whole range of people (I don't mean leaders or managers, but bottom/middle people) who make a career in all those non-profits, para-public and semi-public associations (all of them living mostly from subsidies), hoping from one to another. At least it goes like that in my country, it has developed a lot in the last 30 years.