How Windows Azure Platform is an open cloud platform. What makes it interoperable?
The Windows Azure platform supports popular standards and protocols including SOAP, REST, and XML. Developers can use their preferred programming frameworks including .NET, and PHP, now.
Tools such as Eclipse have been created for PHP developers for building Windows Azure applications. Now external endpoints (inbound traffic) have been enabled to worker a role, which enables applications that receive internet traffic that aren’t running under IIS.
Windows Azure interoperable with Java
At PDC 09, solution accelerator for Tomcat is delivered. Tomcat is an open source software implementation of the Java Servlet and JavaServer Pages technologies. The Windows Azure solution accelerator leverages a PDC09 feature that enable arbitrary processes to bind to inbound service endpoints.
Windows Azure interoperable with PHP
The Windows Azure tools for Eclipse extension builds upon the PHP Development Toolkit (PDT) and integrates Web Tools Platform (WTP) to provide a complete toolkit for Windows Azure web application development.
For more details please refer to the link: http://www.microsoft.com/windowsazure/faq/