The article More than a
Gigabuck: Estimating GNU/Linux's Size is now available, which
examines Red Hat Linux 7.1's source code as a representative
GNU/Linux distribution. It found that it would cost over $1
billion (a Gigabuck) to develop, that it includes
over 30 million physical source lines of code
(SLOC), and that it would have required about 8,000
person-years to develop. Red Hat Linux 7.1 represents over
a 60% increase in size, effort, and traditional development costs
over Red Hat Linux 6.2 (which was released about one year earlier).
Its predominant software license is the GNU GPL.