Closed-source, proprietary, restrictive, exclusive, confidential, private, secretive, inaccessible, guarded, hidden, confidential, classified, patented, restricted, licensed, restricted, protected, and copyrighted are some antonyms for the word "open-source." Closed-source refers to software development where the source code is not available to users, implying that the software's owner retains control over the code. Proprietary refers to software that a single entity owns and controls, and users must pay for access to it. Restrictive software limits user access to the code, while exclusive and secretive software implies that only a specific group of people has access to the software's coding. Other antonyms for open-source implies that the software's coding and data are hidden or inaccessible to people, with confidential and classified software referring to software that is restricted to authorized users only.