Oracle alleges that Google violated its copyright when it put pieces of the crucial Java technology into the Android operating system, which now ships on 80 per cent of smartphones sold. Google’s defense hinges on “fair use,” the idea that it was legally allowed to use Java as it did. 

At the core of the conflict is a fundamental culture clash over “open source,” or code that’s made freely available, without copyright, for any use people can find for it.

Open source is a pillar of the software industry, with a huge and thriving community of developers and companies who rely on it to various extents. Even Microsoft, which spent a long time opposing open source, has come around to embrace it.

But depending which way the jury goes here, Oracle vs Google could have huge ramifications for the way software is built and marketed. It could mean a big payday for Oracle, and a total shift in the industry.

Because successful open source projects have dozens, hundreds, or thousands of programmers improving the same code from different angles, the software can get way better, way faster than any proprietary tool.

It’s also extremely common for companies, especially startups, to take open-source software and use it as the basis for a real commercial product that they’ll actually sell. Open source presents the opportunity to avoid reinventing the wheel, and instead focus on building a viable product.

If Google’s fair-use defence doesn’t work, it could set an alarming precedent for the tech industry.

A ruling against Google here would mean that established tech companies like Oracle could have a new source of revenue: Finding startups and developers that use Java or other technology that could be found to be copyrightable, and claiming damages.

If Google couldn’t mount a successful defense, it’s unlikely anyone else would have better luck.

That’s not great news for software innovation. A big part of open source is free and open communication and collaboration. If developers are worried that they might get sued, the next great open-source software project may simply never get built.