Since I want to protect the privacy of those people (usually you invite them by email address), I wonder whether there's an open-source solution to those mentioned above that I could install on my web server.
- web-based planning for the organizer
- scheduling down to 15 minute starting time and duration
- web-based answer by participants
- invitation by email address
- run on a typical Ubuntu Linux LAMP installation (PHP, mySQL)
- open-source / gratis