The rules about sharing a full-text article depend on a few factors. Broadly speaking, fully open access articles and open access alternative versions of articles can be freely shared with anyone. Articles from subscription journals, where the publisher retains copyright, can only usually be shared with other researchers with whom you intend to collaborate.
Kopernio is a signatory to the STM Voluntary Principles for sharing journal articles (https://www.stm-assoc.org/2015_06_08_Voluntary_principles_for_article_sharing_on_scholarly_collaboration_networks.pdf) which specifically allow for the sharing of articles within research collaboration groups. If you have any concerns about sharing an article, we recommend you speak to your librarian about your institution's sharing policies. You can also check publisher sharing policies that might apply (see e.g. https://www.howcanishareit.com/).
When you share an article via Kopernio the recipient will be able to see your details as the source of the article.