You can use your addition by itself if you want. It's not a derived work in itself, only the combination of the 2 texts is.
Unfortunately this isn't the case.... Check out the numerous cases of fan fiction that don't use a single word of the copyrighted work, but have still been ruled to be derived works.
A Fan Fiction is a completely different problem since it will re-use characters, plot, etc.
A Fan Fiction is a derivative work without being a copy of the original work. It is an adaptation.
Inspired works are now starting to fall under copyright protection.
Since they are only starting to fall under copyright protection, that also mean they did not fall yet !
Copyright law still has limits and we can use very easily use these limits. Not doing so would be a criminal attitude and a renouncement to the values that we are fighting for every day.
This trend started with the inclusions of translations under the definition of derivative works and has been expanding since then....
Translation have always been recognized as derivative works ! Just as well as movies adaptated from books, fanfictions and so on.
We are talking about : (1) the transformation of a text by modifying it word by word, (2) the inspiration from a text.
If Wikipedia must set up a policy, I am pretty sure it is better to base it on actual copyright law rather than on some mystic "what-copyright-could-be".
Enforcement has been previously limited to things like fan-fiction
Fan fiction are a completely different problem.
since it's so difficult to prove if original text was derived or not,
It's not that much.
but the history in wikipedia make it pretty easy to make a good argument where previously it would have been near impossible.
Copyright law in the US needs to be reformed,
No, it need to be applied in a better way.
Jean-Baptiste Soufron Intellectual Property and Contracts