In general, open source refers to any program whose source code is made available for use or modification as users or other developers see fit. (Historically, the makers of proprietary software have generally not made source code available.) Open source software is usually developed as a public collaboration and made freely available
Fear, uncertainty, and doubt (FUD) is a sales or marketing strategy of disseminating negative (and vague) information on a competitor's product. The term originated to describe disinformation tactics in the computer hardware industry and has since been used more broadly. FUD is a manifestation of the appeal to fear. Created by IBM but widely use and abuse by Microsoft.