A gatekeeper provides address translation, admissions control, call routing, authorization and accounting services to an H.323 system defined on the H.323 standard by ITU-T. GnuGk's set of features include: It is covered by the GPL-2.0-only license.

Originally, a proof-of-concept gatekeeper was developed by Xianping Chen, Joe Metzger and Rajat Todi for an experiment.

At the start of 1999, Jan Willamowius convinced the first authors to license their code under GNU GPL and began the project.

It had new architecture for gatekeeper routed mode which can handle thousands of concurrent calls, and introduced full H.323 proxy and Citron's NAT technology.

Among the most active were the team a Mediaways (LDAP), Michal Zygmuntowicz (radius support), Chih-Wei Huang (2.2 redesign), and Simon Horne (NAT features).