Dear Debian, Unicode, Inc. has informed me that they just added the directory http://www.unicode.org/ivd/data/ to the list of directories explicitly mentioned as covered by their license; see http://www.unicode.org/copyright.html#License.
Among other files, that directory contains IVD_Sequences.txt, which emacs (among other packages) uses. The license ambiguity for that file had been a concern for someone. All the best, Paul Hardy