The idea about Hopepunk is, well, it's based around the idea of hope as a radical act. The Powers That Be want you to believe that this is how things have to be, that there's no room for fairness, and we must have an elite minority who lives in luxury while so many die in poverty and squalor. Hopepunk is meant to be a counterpart to grimdark. Grimdark says we are evil, miserable creatures living in an evil, miserable world. Hopepunk holds the mindset of "Yeah, we do bad things, but we are also capable of great sacrifice and love and ultimately, our good traits are far greater than our bad parts."
Or it's more like Solarpunk. While Steampunk is centered around a grim world of mad scientists and polluting factories, Solarpunk operates more on the idea that science can be used to bring about a utopia. Too often, it seems like people are stuck with a dichotomy where they feel we can either have modern technology with all its ills or live like medieval peasants. Solarpunk operates more on, "Okay, why not both? We use the stuff from the past that works and throw out what doesn't work. Meanwhile, we put our heads together, utilize both past and present knowledge so we can have stuff like electricity and Internet, without the environmental destruction." If science wasn't, like everything else, effectively being held hostage by Capitalism, think of what we could develop.
tl;dr, I thought the essay was interesting and worth sharing. Sorry to be all long-winded about it.