@Tattenbach: actually, open source is a wide field. When I started this, license part II.a. fullfilled my universities wants of OS. It's not open to anyone though, simply because then the bad guys would be ever quicker to counteract and we would have to countercounteract even quicker and ...
We're planing on something that'll allow some opening, while avoiding the above problem though...
@jonathanbean: bitman has already given a very good explanation. What I've also seen often is magazines complaining about Spybot not detecting "inactive spyware", which means they've got some spyware files, put them onto their harddisk somewhere, and expect Spybot to find them. The "problem" with that is that Spybot may ignore those while on-demand scanning and will find them only on-access. Which isn't a problem outside of test labs though, since there, those files will be found where they're installed.
An example: Malware ABC installs file XYZ.exe ALWAYS to C:\Windows\ (if it should decide on a different location, the files must be changed to reflect that rule, so all our other criteria, mostly file contents checksums, wouldn't fit either, so whether we use the path or not, new version needs new rules... but using the path as one criteria is faster to detect).
In the test lab, the file may be in C:\MyTestSamples\ (what those labs call "inactive spyware tests" or similar), where we don't look for it. You're still protected, because if you add C:\MyTestSamples\ to the download directories setting, it'll be found during on-demand as well, and if you or anyone else tries to start it, the on-access part will detect and block it. But in a test lab, it fails, and I've seen that that often inflicts the final rating a lot.
PCWorld: indeed asked us about advertising in relation to recent reviews. Not that I would actually say that influenced anything.
And about commercial applications... I wonder if those magazines tested email support... we get so many answers from people who're astonished that their emails were answered within hours, in a time that wasn't matched by any commercial vendor they've mailed so far. We've actually got quite a proud support team there who can't stand any questions left in the inbox and do a great job in really fast replies.