Explaining its strategy, Oracle says in the memo that it "can't do everything. The limiting factor is our engineering bandwidth measured in people and time. So we have to ensure our top priority is driving delivery of the #1 Enterprise Operating System, Solaris 11, to grow our systems business."

It also implied that OpenSolaris compromised its competitive position. "We want the adoption of our technology and intellectual property to accelerate our overall goals, yet not permit competitors to derive business advantage (or FUD) from our innovations before we do," it wrote.

The company will "continue to grow a vibrant developer and system administrator community for Solaris" and contribute code to projects like Apache and Perl, it said. Solaris code already released under Sun's open-source CDDL (Common Development and Distribution License) will keep the same license, it said.

It's the second example this week of how Oracle's strategy differs markedly from that of Sun, and also the second time that Oracle has miffed the open-source community.

On Thursday Oracle said it had filed a lawsuit against Google, charging that its open-source Android phone software violated Oracle patents and copyrights related to Java, another technology it inherited from Sun.