I'd only be concerned about having too much content that can also be found on other websites in one way. Your site won't be "penalized", but Google only wants to show one version in a SERP - and they prefer to rank the original. So your site is less likely to rank for phrases in the quoted materials.
If the duplicated materials are a good service for your visitors, then you might find that showing the quoted material in an iframe is useful. That can help not to dilute the ranking potential of any original content you have on the page.