Since we first started talking about using the browser as an authentication tool in December 2000 OpenSource implementations have started to appear. Here is a list of all the software I know of that implements either a CaptivePortal or an ActivePortal solution.

LiveCD

Open Source

Free (Closed Source)

Instant creation of hotspots for Windows XP or 2000. Works with any wireless router or adapter. No MAC required version available upon request.

Commercial