"Otherwise we are asking the EC to rule on whether Oracle is open source-friendly enough to own MySQL, and that is neither something that an organization like the EC is equipped to answer nor something that it should be asked to decide," he added.
Pamela Jones, editor of the Groklaw open-source blog, suggests that opponents such as Widenius, who recently became an advisor to Microsoft's CodePlex Foundation open-source community site, may be acting as pawns for organizations interested in buying MySQL if Oracle is forced to sell.
"There is a Microsoft shadow in this picture," she wrote.
Crucial to this debate is how the open-source license used by MySQL, the General Public License v2, is viewed.
GPL v2 is used for about half of all open-source apps, including Linux. Created by Stallman, GPLv2 requires anyone who distributes or sells an app based on the licensed code to give away the source code for free.
The "copyleft" provision of GPLv2 would allow developers to easily create and even sell so-called "forked" versions of MySQL if they become dissatisfied with Oracle's handling of it. Indeed, a number of forks for MySQL have emerged in the past two years due to dissatisfaction with Sun's management of the database.
The license provision would serve as a check against Oracle's misuse of its ownership of MySQL, supporters of the deal say.
However, critics like Widenius and Stallman argue that any attempted forks of MySQL could not use a key revenue source -- the ability to sell proprietary licenses of MySQL to software vendors looking to build their own apps using MySQL.
For competitive reasons, many ISVs don't want to share the source code back to the wider community. As such, the GPLv2 has little appeal to such developers.
Meanwhile, because it would own the MySQL copyright and the right to distribute MySQL under dual licenses (GPLv2 and proprietary licenses), Oracle would have the right to sell proprietary licenses to ISVs.
In this context, by forcing all source code improvements to be shared, GPLv2 gives Oracle an advantage open-source forkers, the opponents say.
"One can fork a GPL project (i.e. the code), but one can't easily duplicate the economic infrastructure around it," Widenius wrote in his blog.
Some opponents say they would be appeased if the EU forced Oracle to switch off the GPL to a more permissive licensing arrangement, such as that used for the Apache open source Web server.
"Apache leaves everyone -- developers, users, vendors, etc. -- on equal footing," wrote Matt Asay, an executive at open-source firm Alfresco Software, and blogger for News.com. "The GPL does not. With the GPL, the copyright holder [Oracle in this case} retains effective control."
Piana, who recently joined Oracle as co-counsel to work on the effort to clear the merger, argues that opponents of the deal are overestimating the appeal MySQL would have if the open-source community, or even just the key developers, abandoned it. "A proprietary standalone version of MySQL has no appeal compared to the free software licensed one," he wrote in his blog.
Gordon Haff, an open-source analyst with Illuminata Inc., also doesn't buy the argument that the GPL hurts MySQL. He's in favor of the deal going through. "Oracle's planned acquisition of Sun does inject some uncertainty into the MySQL picture although, in my view, the more frantic handwringing is overblown," he said.