MultiOTP Authentication Server
MultiOTP Authentication server installation and integration guide
Guide Version: 1.0 MultiOTP package at time of writing: 5.1.1.2
Introduction
MultiOTP is a 3rd party, OATH certified open source authentication server for HOTP (UniOTP300 and UniOTP310) and TOTP (UniOTP500 and UniOTP510) with both free and paid versions.
The free version supports unlimited users but the paid version has a variety of additional features: Web GUI interface Automated provisioning of new account (based on Active Directory) High Availability master-slave support (Enterprise Edition) Web API support (Enterprise Edition) free virtual appliances available, including a free lifetime one user licence
Download MultiOTP here: https://download.multiotp.net/multiotp.zip
For more information about paid and free versions and source code, go here: https://github.com/multiOTP/multiotp/wiki