I would recommend that changing to GPL just to gain better ad blocking, which is far from being a primary feature, is probably not the greatest idea if you care about licensing.

> which is far from being a primary feature,

I don't know that I agree. If the adblocking functionality has gaps, then I will likely not use it for reading stories, and if I'm already opening up HN in my browser w/ ublock origin, then I might as well stay there and comment. Reading the article may not be the 'primary feature', but strong adblocking does seem like table stakes.