A Checkfree APL developer is responsible for designing, coding, testing, and implementing applications using APL (A Programming Language) in the CheckFree software environment. They work on creating and modifying financial software solutions, specifically for electronic payment transactions. They also maintain the software, fix bugs, and improve its performance. They are required to understand business requirements and translate them into technical specifications. They also work closely with other team members, such as analysts and testers, to ensure the software meets the needs of the end-users and follows the company's protocols and standards.