MySQL has changed its software licensing terms for MySQL 5.0 and 5.1 to prevent the code being governed by the upcoming General Public Licence version 3 (GPLv3). 

Previous licensing terms offered users a choice between the current GPL2 or any later version.

The company has decided to opt out of GPL3 for now because it wants to gauge the market response to the licence before its release, according to Kaj Arnö, community vice president at MySQL.

"MySQL AB continues to work with the Free Software Foundation for GPLv3 to be the new widespread licence under which free software is licensed," Arnö wrote in a blog posting in December. 

"However, until we get clear and strong indications for the general acceptance of GPLv3 over GPLv2, we feel comfortable with a specific GPLv2 reference in our licence."

Arnö has been part of the committee that created the draft for the licence, and said that he is confident that it will be widely adopted.

MySQL's reasons for opting out from GPL3 are different from those of many Linux distributors, some of which have criticised the licence for its "religious" battle against digital rights management (DRM) technology.

In addition to banning DRM, the GPL3 is deemed controversial because it plans to prevent users and developers of software governed by the licence from launching any patent claims against open source.

While Linux distributors and MySQL have decided to shun the forthcoming licence, it is short on outspoken supporters.

Sun Microsystems has said that it expects to adopt the licence, but has not make any concrete promises. 

Many others are expected to wait for the final version of the document before making a decision about switching.