The BSD 2-Clause License is a simplified version of the BSD 3-Clause License.  This license was popularized by the FreeBSD project and is sometimes referred to as the "FreeBSD License" (see https://opensource.org/licenses/BSD-2-Clause and https://en.wikipedia.org/wiki/BSD_licenses#2-clause).  To clarify that the OpenLayers License uses the BSD 2-Clause License template, this change adds "The 2-Clause BSD License" to the top of our license file.  In addition, this change makes our license a verbatim copy of the template at https://opensource.org/licenses/BSD-2-Clause with only the copyright holders added.  This change is not intended to change the project's license, only to clarify the template used for that license.  See https://lists.osgeo.org/pipermail/openlayers-dev/2011-May/007555.html for the original motion to switch to the BSD 2-Clause License (also known as the FreeBSD License).