Difference between IPortal and iServer Express

The simple answer to differentiate between iPortal and iServer Express is:
iPortal is a web application for browsing and running reports, and the iServer Express is a report server that allows you to deploy, schedule, manage, secure, and run reports

The iPortal is a web application that can be deployed as a .war file into your application server or installed with a Tomcat instance to enable end users to browse for and run reports. Upon seleing reports to run, users are prompted for any report parameters and the report is executed on demand. By default, reports are viewed in a static report viewer, but the iPortal is also the foundation for the BIRT Interactive Viewer and for a web based BIRT designer call BusinessReport Studio which is geared towards end users.

The iPortal runs in two different modes:
1) Workgroup - This is the scenario described above and the report generation takes place on the application server.
2) Enterprise - In this scenario, the iPortal communicates with the iServer Express via web services to allow users to browse, schedule, and run reports (and more). When you download the iServer Express, the iPortal is automatically included and installed.

The iServer Express is a fully functional report server that enables scheduling, security, report design and output versioning, notification, delivery, and more. The iServer Express runs outside the application server to avoid impacting load on the application server.

The iServer Express allows you to generate and view BIRT reports, interactively view BIRT reports, design BIRT based reports over the web, and generate and view e.Spreadsheet reports. There are also options for data integration (EII) within the iServer Express. Each of these are priced independently of each other to avoid having to purchase more than needed.

While iServer Express will likely run on Debian Linux, the certified and supported Linux distributions are RedHat Enterprise, and SUSE Enterprise.