Jonbouy
slartabartfast
The wise thing to do if the file is not critical is to play it safe. There is nothing wrong with warning your friends about such a finding, even if you cannot confirm that it is not false positive. If your antivirus has it right, then you can save them a world of hurt. If your antivirus is wrong, they can take special care to be sure theirs is not just missing it.
Providing you take care not to damage an innocent vendors good reputation for supplying clean files...
I assume that all vendors are innocent, regardless of whether they have infected files for download or not. Unless you are visiting a malicious website, infected files are not deliberately placed there by the merchant, who is as much a victim as anyone. If you are concerned about the "reputation" of the vendor, the best thing you can do is to contact him and let him know what you have found. He then has the option to purge his code, or report the false positive to the antivirus maker and request an exception for his file.
Most false positives that I have downloaded, affect precisely these small operations. With some notable exceptions, a file that millions of people download daily which an antivirus falsely flags will be fixed quickly, or the antivirus vendor will add it to their false positive list. The vendor can put a notice on their website acknowledging that the file is incorrectly flagged by antivirus X, with links to other antivirus scanner results, but the casual user may think this is just part of the scam. This kind of thing is a potential nightmare for the vendor.
Still as a user, I would prefer to have a false su****ion raised than to miss a real virus that my scanner does not catch.
edit Apparently the forum software has decided that I have intended to post a racial slur against persons of Hispanic ancestry cleverly hidden in the noun form of su****ious...er doubtful about the integrity or truthfulness of.