There are millions if not billions of RSS feeds on the Internet. Most are no updated often, but some are. There are many consolidators of feeds as well (search engines being the biggest consolidators). The lesser updated feeds will almost always “love” it if you display their feed to the public (with a reference to them of course). The news feeds that come from paid publications or from consolidators are usually for personal use only.
When using feeds for digital signage in an office environment, it is up to you to verify that the feeds you find are legal to show on your screen. Many feeds are not for commercial use, and finding that statement is sometimes a search for a needle on their web site haystack. If you are just using one or two screens in your organization and you cannot easily see the legal messages, the odds of being sued are probably quite small. If you want to be on the up and up, there are several places where feeds can be subscribed to. Some Internet based digital signage software offers feeds that are provided to paid subscribers as part of the software subscription. You can also get written permission directly from the feed provider. Be sure your permission is written (at least an email) from a VP or higher level person in the company to protect yourself.