Android chief Andy Rubin wrapped up his testimony this morning in the copyright portion of the Oracle-Google trial at the U.S. District Court here.

Google counsel Robert Van Nest picked up from where he left off on Tuesday afternoon, asking Rubin what happened after initial negotiations with Sun Microsystems ended in 2006. Rubin said that the Android team went forward to build the mobile operating system on its own.

“We wrote code ourselves, obviously,” said Rubin. “In developing Android, we assembled it from various pieces.”

Although it is constantly evolving, Rubin commented that there are 15 million lines of source code and “many thousands” of independent files that make up Android.

Also dabbling with the the Linux system among other technologies, Rubin added that Google partnered with companies on open handset lines, paying them for contributions back into Android.

One example of a contribution that Google paid for is the media framework from Packet Video, which is used on Android for decoding video files.

Rubin said that it took roughly three years from inception to completion of Android 1.0 in 2008. He also explained that what was released in 2007 — an Android SDK — wasn’t enough for a smartphone, but rather just enough for third-party developers to write their own apps for Android.

“The SDK allowed the programmer to see the APIs that were in existence on that early date,” Rubin said, noting it would have included some of the Java application programming interfaces in question in this case at that time.

Rubin affirmed that anyone could have seen this as early as October 2007, saying, “All they needed to do was go to our Web site and click the download button.”

However, during cross-examination, Oracle counsel David Boies asked Rubin whether there was any record of anyone at Sun praising Google’s use of Java for Android after the SDK was released. (Boies pointed out that Sun CEO Jonathan Schwartz’s blog post praising Google was after the announcement of Android but before the SDK was released.)

Rubin said there were a few — including conversations with Sun CTO Vineet Gupta — but there isn’t any written record confirming these comments.

When asked if Android application developers are writing primarily in the Java language, Rubin noted that to write an app for Android, it has to include Java. One reason behind that was to have support for legacy applications from third-party partners, such as games from Electronic Arts.

The open-source project Apache Harmony, in particular, has repeatedly been brought up in this trial, serving as a comparative example for Google of using Java APIs on an open-source platform.

“It’s open-source. That’s what’s magical about this,” Rubin remarked.

Rubin acknowledged that there were other companies trying to build upon the Apache Harmony project, but IBM was the only example that Rubin could confirm.

“The whole purpose of that project was to implement a clean-room version of the Java APIs,” Rubin said, adding that there were many other (albeit “uncoordinated”) efforts also trying to do this.

Rubin also explained, “The Apache Software Foundation also has their own version of an open-source license. It’s a small legal document that basically describes your rights as a customer of this open-source project.”

Taking all of this together, Van Nest asked Rubin if he thought at the time that Google would need a license to use the Java APIs. Rubin replied, “We did not believe that we needed a license from Sun.”

Rubin also said that the first time he heard of any violation regarding Android and its use of Java APIs was at the beginning of this lawsuit.

“One of the benefits of open source is providing our work openly and freely is that other people can expect it,” Rubin said, asserting that there’s nothing “hidden” in the Android source code.