First of all, Donut theme is offered officially with Q2A. It's a third party theme. Secondly, Notification Plugin is also not official plugin of Q2A. It's a third party plugin.
Now both the developers have made their products compatible to run smooth with Q2A official release. But if their products are not compatible to each other's product then you cannot force any developer for this. Their work was to make a product compatible to Q2A and they did it. Now if you need some extra work to be done by any developer then off course that developer will demand some money for this, aftera ll this is an extra work for him.
I hope you understand this.