Building a business is about distribution as well as product. My product is pretty good, but my distribution, compared to a large player with an existing user base, is woeful. If I licensed under GPL I would be giving explicit legal permission to any big player (who was open source) to take my product for free, and compete with me solely on distribution.

Licensing my product in the above way wouldn't be good for me financially, and as a result would decrease my likelihood of working full time on Dependabot. Worse still, it would disproportionally decrease my returns from working on the product, as opposed to distribution.

Thanks to copyright law we don't need to hide our codebases in order to charge for our work. That's a great thing, and there should be acceptance of code that is developed in public but without a permissive license. It's a perfectly rational decision, and creators shouldn't be put under pressure to give their development work away for free instead.