Although most open source developers would probably hate to admit it, marketing works. A good marketing campaign can create buzz around an open source product, even to the point where hardheaded coders find themselves having vaguely positive thoughts about the software for reasons they can't quite put their finger on. It is not my place here to dissect the arms-race dynamics of marketing in general. Any corporation involved in free software will eventually find itself considering how to market themselves, the software, or their relationship to the software. The advice below is about how to avoid common pitfalls in such an effort; see also the section called “Publicity” in Chapter 6, Communications.
For the sake of keeping the volunteer developer community on your side, it is very important not to say anything that isn't demonstrably true. Audit all claims carefully before making them, and give the public the means to check your claims on their own. Independent fact checking is a major part of open source, and it applies to more than just the code.
Naturally no one would advise companies to make unverifiable claims anyway. But with open source activities, there is an unusually high quantity of people with the expertise to verify claims—people who are also likely to have high-bandwidth Internet access and the right social contacts to publicize their findings in a damaging way, should they choose to. When Global Megacorp Chemical Industries pollutes a stream, that's verifiable, but only by trained scientists, who can then be refuted by Global Megacorp's scientists, leaving the public scratching their heads and wondering what to think. On the other hand, your behavior in the open source world is not only visible and recorded; it is also easy for many people to check it independently, come to their own conclusions, and spread those conclusions by word of mouth. These communications networks are already in place; they are the essence of how open source operates, and they can be used to transmit any sort of information. Refutation is usually difficult, if not impossible, especially when what people are saying is true.
For example, it's okay to refer to your organization as having "founded project X" if you really did. But don't refer to yourself as the "makers of X" if most of the code was written by outsiders. Conversely, don't claim to have a deeply involved volunteer developer community if anyone can look at your repository and see that there are few or no code changes coming from outside your organization.
Not too long ago, I saw an announcement by a very well-known computer company, stating that they were releasing an important software package under an open source license. When the initial announcement came out, I took a look at their now-public version control repository and saw that it contained only three revisions. In other words, they had done an initial import of the source code, but hardly anything had happened since then. That in itself was not worrying—they'd just made the announcement, after all. There was no reason to expect a lot of development activity right away.
Some time later, they made another announcement. Here is what it said, with the name and release number replaced by pseudonyms:
We are pleased to announce that following rigorous testing by the Singer Community, Singer 5 for Linux and Windows are now ready for production use.
Curious to know what the community had uncovered in "rigorous testing," I went back to the repository to look at its recent change history. The project was still on revision 3. Apparently, they hadn't found a single bug worth fixing before the release! Thinking that the results of the community testing must have been recorded elsewhere, I next examined the bug tracker. There were exactly six open issues, four of which had been open for several months already.
This beggars belief, of course. When testers pound on a large and complex piece of software for any length of time, they will find bugs. Even if the fixes for those bugs don't make it into the upcoming release, one would still expect some version control activity as a result of the testing process, or at least some new issues. Yet to all appearances, nothing had happened between the announcement of the open source license and the first open source release.
The point is not that the company was lying about the community testing. I have no idea if they were or not. But they were oblivious to how much it looked like they were lying. Since neither the version control repository nor the issue tracker gave any indication that the alleged rigorous testing had occurred, the company should either not have made the claim in the first place, or provided a clear link to some tangible result of that testing ("We found 278 bugs; click here for details"). The latter would have allowed anyone to get a handle on the level of community activity very quickly. As it was, it only took me a few minutes to determine that whatever this community testing was, it had not left traces in any of the usual places. That's not a lot of effort, and I'm sure I'm not the only one who took the trouble.
Refrain from giving negative opinions about competing open source software. It's perfectly okay to give negative facts—that is, easily confirmable assertions of the sort often seen in good comparison charts. But negative characterizations of a less rigorous nature are best avoided, for two reasons. First, they are liable to start flame wars that detract from productive discussion. Second, and more importantly, some of the volunteer developers in your project may turn out to work on the competing project as well. This is more likely than it at first might seem: the projects are already in the same domain (that's why they're in competition), and developers with expertise in that domain may make contributions wherever their expertise is applicable. Even when there is no direct developer overlap, it is likely that developers on your project are at least acquainted with developers on related projects. Their ability to maintain constructive personal ties could be hampered by overly negative marketing messages.
Bashing competing closed-source products seems to be more widely accepted in the open source world, especially when those products are made by Microsoft. Personally, I deplore this tendency (though again, there's nothing wrong with straightforward factual comparisons), not merely because it's rude, but also because it's dangerous for a project to start believing its own hype and thereby ignore the ways in which the competition may actually be superior. In general, watch out for the effect that marketing statements can have on your own development community. People may be so excited at being backed by marketing dollars that they lose objectivity about their software's true strengths and weaknesses. It is normal, and even expected, for a company's developers to exhibit a certain detachment toward marketing statements, even in public forums. Clearly, they should not come out and contradict the marketing message directly (unless it's actually wrong, though one hopes that sort of thing would have been caught earlier). But they may poke fun at it from time to time, as a way of bringing the rest of the development community back down to earth.