GatewayScript is what is called a new capability that will be available in the upcoming DataPower firmware version 7.0. A lot of attention has been put into this topic recently and it will be present in at least four different presentations at Impact 2014 by the end of this month.
It does not mean that the available programming languages, such as XSLT and XQuery, were lacking power. The main idea on bringing a new programming language to the table is to leverage common programming skills, speeding up DataPower adoption and making it even more popular.
New ways to debug code have also been made available for the GatewayScript functionality, making it possible to add break points, print variable values, explore stack trace, etc.
Performance is not supposed to be an issue with the new available language, as the code will be compiled, cached and reused on demand. IBM keeps promising wire-speed for processing.
Examples will be provided with the new firmware in order to give us a better idea on what exactly can be accomplished with this new capability. They will be located under store:///gatewayscript/example-*.js.
In the morning of April 15th, Tony Ffrench (STSM DataPower Architect), Tim Smith (DataPower Architect) and Ozair Sheikh (DataPower Product Line Manager), gave a very rich presentation at the WebSphere User Group website, about the new capabilities that will be available on the new firmware version. If you did not have a chance to attend to this webinar, you can download the presentation used by them right here.
To see the official IBM announcement of the new firmware version 7.0, click here.
EDIT: On April 17th, the replay of the above presentation has been made available by the WebSphere User Group website. To watch it, just click here.