osTicket

osTicket is a widely-used, free, open-source support ticket system that turns inquiries from email, phone and web forms into tickets in a simple multi-user web interface, so teams can manage, organise and archive all support requests and responses in one place.

• Open-source alternative to: Zendesk, Freshdesk
• Licence: GPL-2.0 (Copyleft open source)
• Website: https://osticket.com/
• Source code: https://github.com/osTicket/osTicket
• GitHub stars: 4000, forks: 1849
• Topics: helpdesk, support tickets, customer support, ticketing system, business