DFSGLicenses > Lesser General Public License (LGPL)
The GNU Lesser General Public License or LGPL is used by almost all GNU libraries, and many of all FreeSoftware
It's a DFSG compatible license.
You can get a verbatim copy :
LGPL-v2.1 or on your Debian system in /usr/share/common-licenses/LGPL-2.1
LGPL-v2 or on your Debian system in /usr/share/common-licenses/LGPL-2
See also :
http://www.gnu.org/licenses/licenses.html#LGPL GNU's page about LGPL Licenses
Wikipedia's LGPL