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FUDForum is an open-source product which is well supported with frequent releases and attention to details/quality. vBulletin is commercial (but relatively cheap). vBulletin is a "visible source" commercial product. Who exactly develops it is unclear "Our team is all over the world. Our headquarters are located in Southern California. vBulletin Solutions, Inc is a company registered in California, US and a division of Internet Brands."
I am less convinced than Imre that commercial support is necessarily better than open source, at least I think everyone could agree that the best open-source products are better than the worse commercially supported products, so comparisons should be made on a case-by-case basis.
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