If you have any thoughts of making any money of the code that may be a reason to give the license some thought. Anything else, these days, is just a LLM away from getting re-written regardless of whatever license you use. For example there is a service that takes any code, uses one agent to create requirements and another to use those requirements to create a comparable program; the claim is that the second agent did not "steal" your code since it purely worked off requirements. Sure, it likely won't be as good, but it allows someone to take a significant part of your code for themselves. That was, more or less, always there in the past is just that now is near trivial to do.

Also, there are projects that are just fake open source. Like a project I saw yesterday with a restrictive license, but then has a CLA.

• AGPL restrictive copyleft license -- good
• CLA (Contributor License Agreement) — a legal agreement where you grant the project maintainers additional rights over your contribution, often including the right to relicense it under different terms -- not good

So, that project at first sight appears like it is open, but because of the CLA the authors may just take whatever contributions you do to the project and then change it's license.

You're on the open-source community, of course we'll be biased in favour of open source. One thing to point out is that open-source and closed source are both pretty broad categories that cover several licenses. Source available means people can see the code, but there are restrictions to how they can use it. Is there a specific thing you don't want people to do with your code? Do you not want them to edit it for example? Or you're fine with them editing it, but not for commercial purpose ? Any restriction of this type will make it source-available. If you're fine with them doing anything, it's open source. If you want them to mention somewhere that their code is based on yours, it's still open source. And if you want any code made by editing yours to also be open source, that's still open source (that's the idea of the GPL). But other restrictions might make it not fit that category.

I personally usually default to the GPL3, I'm fine with people doing anything with my code except making it non-open source. Well "my code"... It might be a bit presumptious of me, I'm not really a programmer, I've just made a few small and not very useful things. There may be legitimate reasons for not wanting your code to be open source sometimes, but for me the stakes have always been low.

As for whether using Github creates an expectation for Open-Source... Not so much at this point. It's very used by the Open-Source community, but not only. Plus, it's not really open-source itself, so the most purist prefer other git platforms like git-lab, forgejo or source-hut.

Do you want external input and to contribute to society? Open source

Do you want external input but don't want your code used in other projects? Source available (ie open source with very restricted licensing)

Do you not want any of that and just want to do your own thing? Closed source

A good thing to remember is that open source invites both good and bad criticism, as well as help, so it can help you improve but it can also be hard to handle the less than helpful people.

Also, like real life, the more you hide info, the less trustworthy you are. Open source puts you in a default trustable position for many people, while closed source puts you in a default untrustable position.