Add licensing information

Per:

| timl@willow:~$ ldapsearch -h ldap -b ou=people,o=unix,o=toolserver uid=w tsDefaultLicense
| version: 1
| dn: uid=w,ou=People,o=unix,o=toolserver
| tsDefaultLicense: MIT
| timl@willow:~$

the source is licensed under the MIT License.