Judge William Alsup, who is hearing the case, on Thursday upheld an earlier ruling that the email should remain part of the court record. The email, written by a Google engineer, suggests that Google knew it needed a license to use Oracle's Java technology in Android.

Oracle accuses Google of infringing its Java patents and copyrights in the Dalvik virtual machine software in Android. Oracle took control of Java when it bought Sun Microsystems last year.

"What we've actually been asked to do (by Larry [Page] and Sergey [Brin]) is to investigate what technical alternatives exist to Java for Android and Chrome," says the email, from Google engineer Tim Lindholm. "We've been over a bunch of these, and think they all suck. We conclude that we need to negotiate a license for Java under the terms we need."

Google has argued since July that the email is privileged and that it provided it to Oracle inadvertently. The mail was written after Oracle threatened to sue Google for patent infringement, and defendants are not required to disclose communications with their lawyers if they are seeking legal advice about a case.

There are nine versions of the email, including eight drafts that were saved automatically while Lindholm wrote the note. Since he didn't fill in the "to" field or mark the email as confidential until the final draft, Google mistakenly handed the earlier drafts to Oracle during the discovery process. The final email was sent to Andy Rubin, head of Google's Android division, and to one of Google's lawyers.