SIPp as a whole is licensed under the GNU General Public License, version 2 or any later version (copy below).
send_packets.c, send_packets.h, md5.c and md5.h have separate copyright licenses, which apply only to those files.
The following license applies to send_packets.c and send_packets.h only:
The following license applies to md5.c and md5.h only:
All other parts of SIPp are under the following license (or, at your option, any later version of the GNU GPL):