A few months ago, we launched the Plaxo Partner program and our Open API. It's been a great success so far, with over 10 partners already signed up to Plaxo-enable their applications.
When it comes to address books, many companies first take the "build it, and they will come" approach, investing heavily in developing an address book database infrastructure that they then hope their users will populate. Lots and lots of evidence shows that this doesn't work: people don't add entries fast enough to cope with the ever changing dynamics of their network; and import tools are not used because as soon as you import data from another address book, it's out of date: people move, change jobs, get new email addresses and mobile phone numbers.
Plaxo's goal is to enable partners to create complete and accurate address book as well as new sources of revenue, by focusing first on getting complete and accurate data into the address book, and then on keeping it that way. One way we do this is through the Plaxo API and its accompanying tools.
The Plaxo API is accompanied by a set of tools for importing data from most sources of address book information (Outlook, Outlook Express, Yahoo!, Gmail, Hotmail, AOL, etc.). The two together help you create a complete address book on your site that's connected via Plaxo to all the other places your users store data, and to all the other people your users know. It can help grow your business and help you offer new services that use the data.
If you have a site or a service you think needs a connected address book, we'd like to talk with you.
Regarding the open-source "rules", have you considered releasing the models under a Creative Commons license? tranadol