The blog post Drupal vs. Joomla - Fight! pointed me to a discussion on the drupal-devel mailing list about the ohloh.net website which tries to gather some statistics/metrics about the code of Free Software projects. Their slogan:

Explore Open Source

Mapping the open source world by collecting
objective information on open source projects.

You might want to read their Terms of Use, though, which don't sound very open...

Anyway, their stats about Drupal and about Joomla! are flawed (for example) because they seem to include the whole contrib CVS tree of Drupal (not just the core Drupal), which is huuuge. But there's no need to use any fancy website anyway, there are Free Software tools out there which can produce some metrics, too.

The following data is generated using David A. Wheeler's SLOCCount (for the respective tarballs of the current stable releases):

Drupal 4.7.4

Total Physical Source Lines of Code (SLOC) = 8,012
Development Effort Estimate, Person-Years (Person-Months) = 1.78 (21.34)
(Basic COCOMO model, Person-Months = 2.4 * (KSLOC**1.05))
Schedule Estimate, Years (Months) = 0.67 (8.00)
(Basic COCOMO model, Months = 2.5 * (person-months**0.38))
Estimated Average Number of Developers (Effort/Schedule) = 2.67
Total Estimated Cost to Develop = $ 240,198
(average salary = $56,286/year, overhead = 2.40).
Joomla 1.0.11

Total Physical Source Lines of Code (SLOC) = 65,880
Development Effort Estimate, Person-Years (Person-Months) = 16.25 (194.94)
(Basic COCOMO model, Person-Months = 2.4 * (KSLOC**1.05))
Schedule Estimate, Years (Months) = 1.54 (18.54)
(Basic COCOMO model, Months = 2.5 * (person-months**0.38))
Estimated Average Number of Developers (Effort/Schedule) = 10.51
Total Estimated Cost to Develop = $ 2,194,486
(average salary = $56,286/year, overhead = 2.40).

Not that I think these numbers mean anything ;-) Lines of Code is a very, very unreliable indicator for code quality (or anything else, for that matter)...