I don't see what the big deal about this is.
There is nothing wrong with porting someone elses add-on if:
- If the original author is active, ask if you can port it, and then credit the author.
- If the original author is inactive, credit the author.
- Make sure it works.
- Don't do an awful job.
- Don't port something that is downright horrible or overdone.
That is what for the most part I'm trying to say. But the impression I get from people who port other's works is that
they don't follow what you've just listed, or didn't actually care to do so.