Alasdair Taylor's Answer

Under English law, the copying of written content from a website without permission may amount to copyright infringement. If rewriting involves the copying of a substantial part of the original work, then it will likely constitute copyright infringement. If it does not, it will not.

This substantial part copying test needs to be applied in context. I cannot say much more in the abstract.

There will be a separate question of whether the published output of the rewriting process provides good evidence of the copying of a substantial part of the underlying work. A copyright lawyer looking at the original and the copy may be able to give a fairly clear answer to this question.

In general, to avoid copyright infringement when using content from another website, consider getting permission. Sometimes permission will be provided in advance via terms of service or special licence terms. There are other circumstances/ways to copy such content, but all are quite specific – e.g. you can use very old out-of-copyright material without permission.

There are other types of intellectual property which may be relevant, such as trade marks rights, which might also be in play in this scenario.

if in doubt, take professional advice.