In the recent weeks the Kolab specific code in Horde has been significantly restructured to make it more developer-friendly. This cleanup also made it easy to add a small hack that allows you to run Horde with a standard IMAP server that provides no support for folder annotations as a back end.
The Kolab concept is based on IMAP folder annotations but so far the feature is only being provided by the Cyrus IMAP server. In addition the Kolab Server uses some patches in that area which means that you always need a full Kolab Server as a basis for Kolab specific development.
For Horde this means that the other developers have no chance to test the Kolab specific code sections even if they sometimes need to touch these areas. But installing a Kolab server is too much of a hurdle.
So I always wanted to allow running the Kolab code on a plain IMAP server. And ever since Gmail started providing IMAP access I considered the idea of Horde/Kolab on Gmail as a back end a nice toy thing.
Today the code that allows this went into Horde CVS. It is far from finished but it is sufficient to provide you with a demo installation.
You can use standard Gmail credentials there. But please be aware that I could grab these credentials! So you should only use a dummy account in your own best interest.
You'll certainly find many bugs or things that are not working yet but it is of course just a demonstration.
This line of coding is something I won't invest too much time into. It will never get any support from Kolab (as using annotations is the better solution) and I don't guarantee you that the format I'm using stays the same. So if you'd start using the code in a production environment the next upgrade might prevent access to the old data.
The main intention of this is to ease access to the code and allow more people to play with it.
The way things work at the moment is a special Kolab XML format for storing annotations. Each folder gets a single message in this format that carries the UID "1". This message holds all annotation values you'd usually store as folder metadata.
If you want to configure a Horde CVS installation specifically for Gmail you will still need to patch some IMAP parts. For other IMAP servers this might not be necessary.