In the case of IOP owned journals, the authors retain the copyright in the article and grant IOP a non-exclusive licence to publish the article. The position with other journals may vary and is set out in the applicable copyright form.
If an article has been published under the gold open access model, it should have a box with OPEN ACCESS on it at the top of the first page of the article and the licence type (CC BY for newer content and CC BY-NC-SA for older content) at the bottom of the first age of the article.
Articles published under the gold open access model are currently published under the CC BY licence.
Articles published under the gold open access model prior to December 2012 were published under the CC BY-NC-SA licence (you should look at the first page of the article around this time to check which licence the article was published under).
For information on how to request permission, see the permissions section.