You so need to worry about copyright as there are some going silently around to ensure this is done. There is also a curation innitiative I know that votes quality contents on here on steemit; either written or video and they won't move an inch towards plagiarised content. So, to do well; especially if you are not one of those with the "big money" , you might want to maintain some original contents.

Do not forget too that plagiarised contents are flagged on here too... @stephlboy @joshofalltrades