ICU uses the public domain data and code derived from Time Zone
Database for its time zone support. The ownership of the TZ database
is explained in BCP 175: Procedure for Maintaining the Time Zone
Database section 7.

 # 7.  Database Ownership
 #
 #    The TZ database itself is not an IETF Contribution or an IETF
 #    document.  Rather it is a pre-existing and regularly updated work
 #    that is in the public domain, and is intended to remain in the
 #    public domain.  Therefore, BCPs 78 [RFC5378] and 79 [RFC3979] do
 #    not apply to the TZ Database or contributions that individuals make
 #    to it.  Should any claims be made and substantiated against the TZ
 #    Database, the organization that is providing the IANA
 #    Considerations defined in this RFC, under the memorandum of
 #    understanding with the IETF, currently ICANN, may act in accordance
 #    with all competent court orders.  No ownership claims will be made
 #    by ICANN or the IETF Trust on the database or the code.  Any person
 #    making a contribution to the database or code waives all rights to
 #    future claims in that contribution or in the TZ Database.