Lack of organizational policy regarding open source software should be the greatest concern for an organization that uses open source software applications, as it may expose the organization to legal, security, and operational risks. Open source software is software that is freely available and can be modified and distributed by anyone, subject to certain conditions and licenses. An organizational policy regarding open source software should define the criteria and procedures for selecting, acquiring, using, and maintaining open source software, as well as the roles and responsibilities of the stakeholders involved. Lack of reliability, lack of monitoring, and lack of professional support are not the greatest concerns, as they can be addressed by implementing quality assurance, configuration management, and community engagement practices for open source software. References = CRISC by Isaca Actual Free Exam Q&As, question 214; CRISC: Certified in Risk & Information Systems Control Sample Questions, question 214.