Even if you look at industry contributions, this is not actually why code is open sourced.

The individual incentive is to open source code to show the rest of the industry what you have been able to build, with personal returns to you if it actually gets meaningful adoption.

And companies are willing to go along with this because infrastructure projects are not actually a source of competitive advantage and they would rather co-operate on keeping input costs low, and also not get stranded on a tech island with totally custom tooling for everything. You also derive some marginal benefit if the OSS code actually gets used by others since you still control the project direction.

And then separately you have OSS first companies that are hoping that being OSS lets them gain a marketing/sales advantage with developers who care about that.

These incentives remain the same even if there is no meaningful surplus.

Exactly. For individual, hobbyist developers, just showing their work might already be a strong incentive but for profit seeking companies, the motivation to open source their code hinges on tangible benefits like you said. We're developing a digital platform with a marketplace for 3rd-party developers to contribute and make money from their contributions, at one point we had to decide whether we should open source our code, the pros and cons in doing that etc. And we came to conclusion that, in our case, by proving both cloud and open sourced version will definitely help drive more attention to our cloud offerings and attract more developers to provide/sell their own applications on the marketplace. However, we have to keep our focus on our cloud version first and delay the release of the open source version for at least 1 year or until our cloud gets enough traction/attraction. I don't know if this will work out well in the end but we have got to try.

I was around when it started and at that time it was ideological, ala Stallman. Those participating were some of the best programmers that have ever lived. Much later college students got involved and their motivations were totally different - they were looking to do something that would help them land a job, build a reputation, or make money.

It still is, for some, ideological. I know plenty, whose day to day job isn't even software, doing this.

Now, just as food for thought: I believe the mere existence of FOSS promotes a more sustainable economy!

It regulates, in a way, commercial software. You cannot be more user hostile / be less convenient and/or provide lesser of a service than FOSS alternatives! Convenience is at the end of the day, the reason for someone to choose a tool. Software is a tool. Greater convenience of use generally promotes greater productivity when using the tool.

Many of us already make the logical decision to use FOSS to not have to deal with the rising user hostility of consumer grade software. Maybe because, we as developers, have the know how to minimize the rough edges or have the same type of brain of the creator of the software in question, and think: "Indeed! the decisions made on the interface, the flow of using the tool, whatever else, are sane and make the most sense!!!". Hinting here, that the incentives of FOSS do not necessarily align with the preferences of a consumer, which is sometimes a good thing.

Nevertheless! The freedom, as in free, not as in beer, represents a bar of sympathy, of respect for the user. One that has the potential to minimize user hostility of commercial software for fear of losing that customer. Users are beginning to be more savvy than ever, they've been burned a lot before, and/or were born in the midst of the digital age. The barrier of FOSS, its arguable lack of convenience, is shrinking every day. And, in such a way promotes an economy where you have to respect your customer. One that is then, more resilient and sustainable.

Weren't Stallman et al. college students too ?

College students, hobbyists, enthusiast outsiders with no formal education.

It's originally the product of amateurs, in the original sense of the word: people doing something for the love of it.

you mean like curl, samba or sqlite?

I mean like Linux, and Unix tools like vi. “College students” is maybe too limiting, but a large number of early open-source projects came out of university environments.

yes, linux also is a good example of a student project that addressed a lot of enterprise-level use cases