"CodeCount" toolset for counting SLOC.
  http://sunset.usc.edu/research/CODECOUNT/
Covers C/C++/Ada/Java and a few others, but
NOT Python, TCL, Perl, or LISP.
I used this to count C, C++, and Java code.
These tools are under a GPL-like license, but it's NOT the GPL.
See their website for more info.

A huge list of tools is at (mostly big $$):
  http://www.concentricmc.com/toolsreport/5-3-2tools1.html
which extracts from this 1995 paper from STSC:
  http://www.stsc.hill.af.mil/CrossTalk/1995/apr/Metrics.asp

Another list:
 http://www.qucis.queensu.ca/Software-Engineering/toolcat.html#label181

USC tools (inc. CodeCount) and info on COCOMO II is at:
  http://sunset.usc.edu/available_tools/availabletools_main.html


Software Metrics: An Analysis of the Evolution of COCOMO and Function Points
Roger E. Masse
University of Maryland
July 8, 1997
http://www.python.org/~rmasse/papers/software-metrics/
(good overview paper)