Sorry, I'm not sure that publishing a paid app source code would be a good idea. There is a chance that somebody will publish the same app under different name. Somebody has already published a crack for it. And another Safari app already reuses some code from Dark Reader for Chrome.
You know, some Apple developer can also put some malicious code into Safari, but for some reason you trust them and use their browser, even though they used to slow down older iPhones without a warning, forcing users upgrade to newer devices. Who knows what they will do the next time.
There was a long discussion regarding this review https://www.reddit.com/r/apple/comments/9y0s2a/dark_reader_d...
You know, some Apple developer can also put some malicious code into Safari, but for some reason you trust them and use their browser, even though they used to slow down older iPhones without a warning, forcing users upgrade to newer devices. Who knows what they will do the next time.