Saying they share a common enemy, Sun Microsystems' chief scientist Bill Joy told open source advocates that they must work together. "Let's continue to find new ways to stand on each others' shoulders rather than stepping on each others' toes," Joy told attendees of the O'Reilly Open Source Conference in Monterey, California, on Tuesday. Without ever mentioning the word "Microsoft", Joy detailed some of the troubles Sun had trying to protect Java from being thwarted by the software giant. He said executives figured that Microsoft would do whatever it wanted with Java, but they decided to draw up a contract anyway in case they needed to seek legal protection for the software. Two years ago, Sun sued Microsoft for illegally tinkering with Java and eventually won a temporary injunction preventing the company from shipping some products. But on Monday, a federal appeals court suspended that ruling and asked the judge who issued it to explain why he chose to consider the case under the broader copyright laws rather than contract laws. Joy said his company was now looking to shield its products through stronger methods such as copyrights rather than relying on contracts. Conference organiser Tim O'Reilly acknowledged Joy was a controversial pick for a keynote speaker because his company sells proprietary software. But Joy explained to the audience that Sun was trying to take the best of both the open-source and proprietary worlds and synthesise them into its community licensing agreement for Jini. Joy said strengths of open-source software include that it's open, that more developers can work on it, that companies don't rely on a single provider for fixes, and that the boundaries are flexible. But he said some of the drawbacks of open source include: no guarantee of quality from a single source; limits to financial gains; and something he called a "reintegration bottleneck", which could fragment the product. He said the bottleneck happens when software becomes so successful, drawing so many contributions, that it becomes daunting -- and even impossible -- to wade through all of them and decide which changes make it into the product. Furthermore, he said, many companies are concerned about the compatibility of open-source software. "They actually want someone they can yell at" when things aren't compatible, Joy said. "They really want someone to finger and harass." Joy also ran through some of the aspects that make proprietary software licensing appealing to Sun, including that it protects intellectual property, and it provides for one owner and brand control. However, he said proprietary licensing often leads to slow development, badly timed releases, limited quality and the existence of one monopoly provider on which everyone depends. To develop its community licensing for Jini, Joy said his company looked to Visa, which managed to get banks all over the world -- including many that wouldn't normally work together -- to share information. He said the community license is based on sharing code and bug fixes, but it also requires compatibility testing for non-research users and lets companies add proprietary features as long as the open the APIs. Joy said the company is still working on developing the model and will hash it out at a conference in Annapolis, Maryland, 17 to 20 October.