Under the misleading title of Assessing the risks of open source. the METAGroup has a report on the use of Open Source Java code in commercial environments. Despite the title the actual article is fairly positive.

It includes the following quote: By 2006/07, the cycle of movement between open source and standards will be common, and 80 percent of organizations developing with Java will make some use of open-source products. I really surprised that it's not higher already. For instance if you use WebLogic or WebSphere you're already using code from Jakarta. In fact I think it would be pretty difficult these days to put together a Java project of any size without including some open source code. Some things money just can't buy anymore, for instance where would you go to get an XML parser if you had to pay for it? In this situation the alternative to open source is writing it yourself, and that's certainly not efficient, and is more error prone.