During our Web site classes at the Center for Nonprofit Excellence, there are always questions about Web site rules. Basically, attendees want to know when and if it's OK for a nonprofit to link to another Web site, add a logo, post others' PDFs, etc.
If you were writing a book, you would think twice about copying text and pictures to place it in your own book. But, the Internet is so free and open that it makes you feel like all content is available for use.