I can understand given how big it has gotten and how much of his time it now takes up that last Inktober there was official merch and products, such as a subscription art supplies box (can't remember which one). I also saw people using those boxes and finding them very useful if they weren't familiar with ink or even if they were because it made it feel more fun and inclusive for them. I think this is a great idea, especially since as it gets bigger I feel more people are posting and less people are interacting so it can start to feel like your shouting into a void.
Since there is now officially approved products I can also understand Jake's desire to protect people from cheap knock offs. No one wants a new person to purchase a poorly made sketchbook thinking it's an official and thus good sketchbook for inking.
Likewise as Inktober becomes more famous it would be very bad if someone using the official Inktober logo went and sold an artbook full of disgusting hate art. Making it seem that it is officially supported by Jake and Inktober.
As I understand it from his official statement. Your welcome to take commissions, sell art books etc. Just don't suggest that they are official products approved by Jake and the Inktober team, eg don't use the Inktober logo. And this I see as fair enough.
What I did have a problem with was that Jake didn't inform the community that he was planning to do this or the new guidelines beforehand. I think a lot of this could have been avoided if he had been more transparent from the start. However I am not a lawyer and there might be a good reason he didn't.