License for the tzdata information

[Edwin Groothuis]

For all the years I have never worried about this, but today I got an email in
my mailbox asking me "Since this is vendor imported data, we would like to
register under which license this data is distributed.".

Unfortunately I got not much info from Wikipedia, the tzdata or the tzcode
files. The tzcode says "This code is in the public domain", but the tzdata
doesn't have it, just a "This information is by no means authoritative".

So... is there a license under which the tzdata is distributed?

Edwin