2004 Keywords libre software, Debian, GNU/Linux, libre software engineering, lines of code, SLOC, COCOMO Legal Notice Copyright (cc) 2004 Juan José Amor, Gregorio Robles and Jesús M. González-Barahona size. It is also shown that if Debian had been developed using traditional proprietary methods, the COCOMO model estimates that its cost would be close to $6.1 billion USD to develop Debian 3.0. In addition releases, from 2.0 to 3.1 (see [Robles2004]). ### 4.4 Effort and cost estimations Using the basic COCOMO model [Boehm1981], the effort to build a system with the same size as Debian 3.0 can be estimated