Koha is a full-featured open-source ILS. Developed initially in New Zealand by Katipo Communications Ltd and first deployed in January of 2000 for Horowhenua Library Trust, it is currently maintained by a team of software providers and library technology staff from around the globe.
I have been a Koha developer since 2005, when I became a full time employee of the Crawford County Federated Library System, and the Meadville Public Library. Since that time, I have contributed a number of features and bug fixes to the project, as well as creating the Koha Offline Circulation utility, and creating the Koha Virtual Appliance.
The Koha Offline Circulation desktop application is the most fully featured way to handle offline circulation with Koha.