Google Session at Cloud Expo

Apple is beginning to know how Xerox PARC felt.

Like Apple did to PARC, Google has lifted from Apple again this time on behalf of Google Apps and set up a Google Apps Marketplace where third parties can sell business programs that integrate with Google Apps to the two million companies and 25 million users that have reportedly adopted Google Apps in the last three years.

The marketplace, which will irritate Microsoft, launched Tuesday with some 50 programs from companies like Intuit and Atlassian and more reportedly coming from companies like NetSuite and SuccessFactors. Skytap is kicking in its cloud.

Google appears to want a $100 listing fee and 20% of the take “in return for the streamlined purchase and install process and integration features exclusive to installable apps.” It will be setting up a billing service that manages the share fees and offers a unified bill for all purchases. Until then there’s the existing billing and payment mechanism.

Google retains approval rights.

An app can be hosted on the platform of the developer’s choice and integrated with Google Apps using available APIs.

Google says a third-party cloud app must have single sign-on with Google Apps via OpenID, and can have OAuth-authorized access to Google Apps data and access from the Google Apps’ universal navigation bar.

Google says it’s “often asked when we’ll offer a wider variety of business applications – from accounting and project management to travel planning and human resources management. But we certainly can’t and won’t do it all, and there are hundreds of business applications for which we have no particular expertise.”

Still it’s chary of inflicting a “fractured experience” on users where they have to remember multiple passwords, cut and paste data between applications, and jump between multiple interfaces to complete a simple task.

So once these third-party applications are installed on a company’s domain, they work like native Google applications. They can interact with Google’s calendar, e-mail, document and contact data, be managed from the Google Apps control panel, and opened from inside Google Apps.