On Developerforce.com, Architecting a Commercial Application it says:

Note: Apex Classes exposed as Web services in an authorized managed package are NOT publicly accessible in Group and Professional Edition, even with the special authorization. However, Apex Classes that make Web service callouts to external services will work in Group and Professional Editions.

Non-native apps, known as composite or client apps, typically use Force.com, Salesforce CRM and another source for data, logic and UI outside of Google, Amazon, and Facebook. These apps typically rely heavily on the Force.com Web services API to integrate with Salesforce CRM apps or the Force.com platform. These apps can also be published to the AppExchange. If you want to publish your composite or client app to AppExchange, eligible partners can request a clientID that you can include in your SOAP headers, allowing you API access to Professional Edition customers, once you have passed security review. This grows your potential customer base as Professional Edition customers do not normally have the API feature enabled. Visit the Security Review page for more details. 

http://wiki.developerforce.com/page/Architecting_a_Commercial_Application

I have two questions:

1. What are the qualifications for being an "eligible partner" that can request a clientID?

2. Our composite app will need to obtain data from each customer's CRM environment, post that data to our SOAP web service, and then our application residing outside of Force.com will post data to our Force.com app.  Will this work for Professional Edition customers?

Hi,

Unable to fetch and save Force.com Components to Project: com.salesforce.ide.api.metadata.types.Metadata$JaxAccessorF_fullName cannot be cast to com.sun.xm.internal.bind.v2.runtime.reflect.Accessor

Abort or Continute Force.com project creation?

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while i am creating a new force.com project i got this error: can u please tell me why this error came. i downloaded eclipse and added force.com ide.... when i try to creating a new force.com project i got this error... and i am able to create a force.com project but not getting all existing classes and pages. And not added my new page or class content to the sever when i save. Is it required any other software installations?