OneTime is in the public domain.

If you need a real license, contact Karl Fogel <kfogel@red-bean.com>,
the author.  He'll be happy to give you a copy of OneTime under any
DFSG-compliant license you want, although that will not change its
public domain status.  For more information on DFSG compliance, see
http://www.debian.org/social_contract#guidelines.