It's not "technically" legal, it's fully legal in every sense. And using someone's code for a purpose they explicitly allowed is about as far from morally reprehensible as it gets.

If you don't want people to base closed source software on your work, then you shouldn't be granting them a license that explicitly permits them to do exactly that. AGPL is an option if that is what you want.

The rules of the game are known at the start.

If the scriban people didn't want that to happen, they could have used a license (e.g., GPL) that prohibits it.

Some of us use BSD or MIT licenses precisely for that reason. I'm happy if someone uses my MIT-licensed code in a commercial product. That's why I chose that license.

It's not "morally reprehensible" in any way.