This package is under the GNU GPL version 2, or any later
version at your option.
On Debian system, the GPL is available in 
/usr/share/common-licenses/GPL-2

partman-auto-crypto mostly uses shared code from partman-auto-lvm and
partman-crypto. The only file with some substantial additional code is
autopartition-crypto written by David Härdeman <david@hardeman.nu>.