It is courteous and common practice to acknowledge the creator of a work which you intend to use. OER are no exception. Some OER, which are in the public domain, may be out of copyright or the creators may have waived their rights but you should still give credit to the originator(s) of the work. OER with open licences (e.g. Creative Commons) still preserve the creator’s copyright while clearly indicating how the material can be used (see the section on the 5R permissions).
Learn the basics of how to attribute resources correctly. Take this short course from New Media Rights on how to attribute correctly.
As an educator or learner, you may need to use material you found on the Internet in class or in your own work. Bear in mind that resources found on the Internet do not necessarily become part of the public domain (outside copyright law). You may discover that there are restrictions on what you can use and how you can use it. This can lead to confusion and time wasting. This is illustrated in a report from Communia, an advocacy group on improving access rights to material in the public domain. The report entitled Copyright and Education in Europe: 15 everyday cases in 15 European countries gives typical use scenarios of public domain resources in teaching and learning. It demonstrates the impact of differing national copyright legislation on educational practice (Ireland is not included in this study).
A useful overview of how Irish copyright law and open licensing applies in digital teaching and learning is available in this video (1:01 mins.) from Darius Whelan, UCC and Catherine Cronin, National Forum on Teaching and Learning.
Accompanying resource on Irish copyright law and open licences compiled by Darius Whelan (UCC) and Catherine Cronin, NFTL.
This infographic from the American Library Association (ALA) (2020): Creative Commons for Educators and Librarians illustrates the differences between public domain and openly licensed OER. It clearly describes the different types of CC licences and their permissions for use.