Please answer the following question: Information: - Information is that which informs. In other words, it is the answer to a question of some kind. It is thus related to data and knowledge, as data represents values attributed to parameters, and knowledge signifies understanding of real things or abstract concepts. As it regards data, the information's existence is not necessarily coupled to an observer (it exists beyond an event horizon, for example), while in the case of knowledge, the information requires a cognitive observer. - Daniel Julius Bernstein (sometimes known simply as djb; born October 29, 1971) is a German-American mathematician, cryptologist, programmer, and professor of mathematics and computer science at the Eindhoven University of Technology and research professor at the University of Illinois at Chicago. He is the author of the computer software programs qmail, publicfile, and djbdns which he released as license-free software, later as public domain software. - The term public domain has two senses of meaning. Anything published is out in the public domain in the sense that it is available to the public. Once published news and information in books is in the public domain, although they may also be copyrighted. In the sense of intellectual property, works in the public domain are those whose exclusive intellectual property rights have expired, have been forfeited, or are inapplicable. For example, the works of Shakespeare and Beethoven, and most of the early silent films, are all now in the public domain by either being created before copyrights existed or leaving the copyright term. Examples for works not covered by copyright which are therefore in the public domain, are the formulae of Newtonian physics, cooking recipes and all software before 1974. Examples for works actively dedicated into public domain by their authors are reference implementations of cryptographic algorithms, NIH's ImageJ, and the CIA's "World Factbook". The term is not normally applied to situations where the creator of a work retains residual rights, in which case use of the work is referred to as "under license" or "with permission". - License-free software is computer software that is not explicitly in the public domain, but the software owner has not made explicit the terms of the license which makes the software fully copyright protected according to the Berne convention. - qmail is a mail transfer agent (MTA) that runs on Unix. It was written, starting December 1995, by Daniel J. Bernstein as a more secure replacement for the popular Sendmail program. Originally license-free software, qmail's source code was later dedicated in the public domain by the author. - In computing, source code is any collection of computer instructions, possibly with comments, written using a human-readable programming language, usually as ordinary text. The source code of a program is specially designed to facilitate the work of computer programmers, who specify the actions to be performed by a computer mostly by writing source code. The source code is often transformed by an assembler or compiler into binary machine code understood by the computer. The machine code might then be stored for execution at a later time. Alternatively, source code may be interpreted and thus immediately executed. - Sendmail is a general purpose internetwork email routing facility that supports many kinds of mail-transfer and delivery methods, including the Simple Mail Transfer Protocol (SMTP) used for email transport over the Internet. - vpopmail is a free GPL software package , to provide a way to manage virtual e-mail domains and non / etc / passwd e-mail accounts on qmail mail servers . Originally developed by Inter7 , it declined in use along with Qmail . - Computer software, or simply software, is that part of a computer system that consists of encoded information or computer instructions, in contrast to the physical hardware from which the system is built. - Unix (trademarked as UNIX) is a family of multitasking, multiuser computer operating systems that derive from the original AT&T Unix, developed starting in the 1970s at the Bell Labs research center by Ken Thompson, Dennis Ritchie, and others. What object entity has the relation of 'instance of' with the subject 'vpopmail'? Choices: - case - code - collection - computer - convention - cooking - data - december - delivery - facility - family - free software - information - intellectual property - internet - license - machine - mail - mail transfer agent - october - part - programming - property - public - reference - research - research center - science - sense - software - term - time - transport - two - understanding - university
A:
free software