I’m changing the license on most (maybe all) of my active open-source projects, largely because the MIT license does not have as many blanks that have to be filled in as the New BSD license and the language is a bit simpler. To the best of my knowledge, any rights granted under the New BSD license are also granted under the MIT license, so this is really more of a housekeeping/paperwork issue than a conceptual or substantive change.
If this is of concern for some reason, for the things that were under BSD license and no longer are, the version-controlled repositories still have older versions that are BSD-licensed.
