If MacPorts cannot fetch a binary archive, it tries to build from source instead. Your log shows that your (very old) system is having trouble fetching the source because of certificate verification:
:notice:fetch ---> Attempting to fetch tor-0.2.6.9.tar.gz from https://www.torproject.org/dist/
:debug:fetch Fetching distfile failed: SSL certificate problem, verify that the CA cert is OK. Details:
error:14090086:SSL routines:SSL3_GET_SERVER_CERTIFICATE:certificate verify failed
I doubt this is a problem with the tor
port itself. Please ask on macports-users for help debugging your certificate verification issue.