This is a copy of the [PGP "biometric" word list][], which actually comprises two lists, each with 256 entries each. (One contains only two-syllable words, and the other contains only three-syllable words.) The words were selected in 1995 to be as phonetically distinct from one another as feasible.
The Wikipedia entry describes the lists as being licensed under the [GNU Free Documentation License][], although I have no awareness of any publicly available primary sources stating this. The underlying source code for PGPfone, which was the motivation for the list, [is licensed MIT][].