L'âne (aka L'anePOS) is a (GPL'ed) point-of-sale (cashregister) and backoffice program for retail businesses and restaurants written in Perl on Linux/Unix. It uses PostgreSQL for backend storage.
SQL-Ledger is a great application but it lacks some speed when you want to use it as a cashregister in some retailer stores. SLpos address this issue and provides a simple but fast interface to be used on front-end side of your SQL-Ledger system.