LedgerSMB and related packages are available here for Debian v7 (wheezy), Debian v8 (jessie), and others as necessary or requested.
|deb https://apt.ledgersmb.org/ jessie main|
|deb-src https://apt.ledgersmb.org/ jessie main|
This package repository uses a key to sign the Release files for each of the distibutions that are available here. This allows apt-get/aptitude/etc to operate without an error, once the key from here has been imported or otherwise made available to your system.