Caught in a firestorm of criticism in the blogosphere and online forums, officials at Sun Microsystems are now saying that some upcoming online backup features may not necessarily be made available only to paying users of the MySQL open-source database.

In multiple posts Thursday and Wednesday on the Slashdot Web site, Marten Mickos, former CEO at MySQL AB and now senior vice president of Sun's database group, defended the plan to offer what he described as "high-end add-ons" to MySQL Enterprise customers only -- not to users of the free MySQL Community version. But Mickos added that Sun officials "have not yet decided under what license we will release those add-ons (GPL, some other FOSS license, and/or commercial)."

That means MySQL may end up doing one of three things, a spokesman confirmed via e-mail Thursday: continue on its path of making the add-on backup features and their source code available only to paying customers; offer just the source code to nonpaying users, who then would have to compile the code and do other work to activate the features; or make the add-ons available to all users, paying or not, in a free and ready-to-use fashion.

Mickos and Zack Urlocker, another former MySQL executive who now is vice president of database products at Sun, also promised in separate blog posts that the core online backup capabilities being developed for the MySQL 6.0 release will be made available to all users under the GNU General Public License, no matter what the final decision is on distribution of the add-ons.

Urlocker wrote that "everyone" needs the basic backup features, whereas "many or perhaps most community users" won't require the add-ons, which will provide additional data compression and encryption capabilities as well as native drivers tailored for specific data storage engines.

MySQL is one of the most popular open-source technologies, as shown by its status as the "M" in the LAMP stack of open-source software. But Sun, which acquired MySQL in February for US$1 billion, is facing a litany of emotional charges from some MySQL users and other open-source advocates over the plan to reserve some features for paying customers -- with some critics claiming that the company is betraying the community that built up the database to its current level of popularity.

The new plan was detailed during meetings at MySQL's annual user conference in the US this week. But even with the conference going on, Mickos has posted a total of nine comments about the controversy on the Slashdot site thus far, defending and explaining the company's decision, which he said predates Sun's purchase of MySQL.