Vendors, are your really open source ?

The more I'm using and following the open source products, the more I found complex to choose the right one. Only for one think : the famous license. It is so complex to understand and see the differences between products and I expect that managers have more difficulties to understand. Many companies are saying to support the open source model but what does mean "open source vendor" ? Is it not a paradox ? Many vendors provides dual license or modify well know licenses. For exemple, a vendor are free to use the Mozilla license and just add new paragraphs which are not really compatible with the original idea. So, Keep in mind to review this point before taking your final decision. I would like to suggest to read an excellent summary on that topic from Seth Gottlieb (see on his blog : http://contenthere.blogspot.com/2007/01/commercial-open-source.html).