Developers create applications based on the engine and run them through Google, which hosts the applications and provides storage.
The search giant is set to launch the service on 29 May at its I/O developer conference in San Francisco. The App Engine programme had previously been limited to a group of 10,000 developers.
Google also revealed exactly what it will cost developers to use the service. All accounts will be afforded a free storage quota of 500MB and five million page views per month.
Beyond this, developers will be charged for each additional gigabyte of storage and CPU hour over the allocated amount.
The company hopes that the tool will increase developer interest in cloud computing as well as spur a new generation of more powerful browser-based applications.
"After years of competition among platforms, the web has won because it's open, ubiquitous and there's a passionate community working together to move it forward," said Vic Gundotra, vice president of engineering for Google's developer products.
"Openness is great for developers and users because it knocks down hurdles to building great applications, and speeds the next wave of innovation by sharing good ideas.
"The web does not depend on any one API or tool or product, from Google or anyone else."