"Owe" is a very strong word and can quickly get people into trouble once you start trying to break down human interactions into transactions where certain thing

"Owe" is a very strong word and can quickly get people into trouble once you start trying to break down human interactions into transactions where certain things are owed. Part of this is because to owe something is to indicate some level of force to cause a person to comply. It touches on topics of forcing a person against their will. I'm not saying that it is wrong, but that it makes people extremely uncomfortable and can even lead to people attacking your character for trying to do such a breakdown. I think what we are running into here is a matter where different groups have different expectations of what is owed and why it is owed, but due to the difficulty of talking about what is owed to others makes it hard for us to verbalize or sometimes even concretely conceptualize what we are talking about. There are also different extents one can owe something (legal being the most extreme, as you will be forced to by the courts with possible violence if you don't). If a one of the parents tried to get a court to order you to teach the class on penalty of contempt of course, would you find that reasonable? This sounds quite extreme, but there are plenty of cases of owing someone something that the court does enforce in a similar manner. My guess is that you would find such an reaction unreasonable to an outrageous degree, but would find far less extreme enforcement measures (such as being disappointed) as being reasonable. I would even go a bit off topic and say that this level of being owed is proportional to the payment you receive. As a volunteer you likely get no money, but are still 'paid' in social recognition. So you can owe something on the level of being disappointed, but not on the level of court order. So what level does a project maintainer owe others and why. And what do those others owe them in return?