I'm intrigued by this statement: The original code didn't come with an open source software licence, so I am unable to share my changes.
The original blog post[0] doesn't share a link to a full codebase that I can see, and I can't find anything with a quick google. (Although it may have been removed subsequently?)
I assume code snippets in a blog post, and/or a repository without an explicit license, are covered by copyright, hence the caution; can anyone advise when/how it would be reasonable to take someone's concept, rework the code (as appears to have been done here) and then reshare?
(Author here) There used to be a GitHub repo - but it has subsequently been removed.
Normally, I'd be comfortable sharing snippets under the UK's copyright "Fair Dealing" exemption - but my changes are so tightly integrated into the original code that it doesn't seem right.
Additionally, as I say, my changes are fairly trivial. Read a JSON file, scale an image, stitch it together. It's the sort of thing you can throw together in an afternoon.
As for how much you need to change for it to be reasonable to share, it does rather become a "Ship of Theseus" problem. You'll need to be guided by your own ethics and the laws of your country.
The original blog post[0] doesn't share a link to a full codebase that I can see, and I can't find anything with a quick google. (Although it may have been removed subsequently?)
I assume code snippets in a blog post, and/or a repository without an explicit license, are covered by copyright, hence the caution; can anyone advise when/how it would be reasonable to take someone's concept, rework the code (as appears to have been done here) and then reshare?
[0] https://blog.pixelmelt.dev/kindle-web-drm/