Google committed a major transgression by only including support for a subset of Java classes in its App Engine development platform, according to Sun Microsystems' chief open source officer, Simon Phipps.
"Whether you agree with Sun policing it or not, Java compatibility has served us all very well for over a decade," Phipps wrote in an April 11 blog post.
"That includes being sure as a developer that all core classes are present on all platforms. Creating subsets of the core classes in the Java platform was forbidden for a really good reason, and it's wanton and irresponsible to casually flaunt the rules."
Phipps also criticized Google in a Twitter post, saying the company's move "laughs in the face of a decade of compatibility".
It is unclear whether Sun will attempt to apply pressure to Google. Phipps characterized his own remarks as non-official.
"This isn't something I could comment on on Sun's behalf," he said via e-mail Monday. "My personal comments come purely from my long association with Java topics."
Sun officials could not immediately be reached Monday.
Google, which announced App Engine's Java support on April 7, has posted a list of the Java classes which App Engine applications can access.
The company might be planning to add more classes to the list, as it is calling the Java support "an early look," and has invited 10,000 developers to begin using it.
Google is also building out a page dubbed "Will it play in App Engine," a list of compatible Java tools and frameworks.
A Google spokeswoman provided the following statement in response to a request for comment: "We provide a Java 6 runtime environment in a secure sandbox. We committed to having as many standard Java tools and frameworks work with App Engine as possible, and hope to improve the product through the feedback of developers during our Early Look."