Following the launch of the Open Database Alliance some people have assumed that it is only a matter of time before MariaDB becomes the de facto replacement for MySQL.

That assumes that Oracle will allow the development of MySQL to stagnate, either deliberately or through neglect - something that we have expressed our doubts about, but even if that were the case it appears that the GPL (or more to the point MySQL’s dual licensing strategy) may restrict the potential for MariaDB.

Curt Monash recently raised the question of whether closed-source storage engines can be used with MySQL (and, by extension, MariaDB) without a commercial relationship between the vendor and MySQL/Sun/Oracle.

The issue is particularly relevant because if the answer is “no” it would limit the ability of MySQL storage engine providers (such as Kickfire, Infobright, ScaleDB, Tokutek, Calpont) to switch their allegiance to MariaDB.

Mike Hogan, CEO of ScaleDB, has suggested (in the comments to a previous Curt post) that it is hypothetically possible to link a proprietary storage engine to a GPL database without the storage engine having to also be released under the GPL by using a database-independent “OSS glue layer that makes calls to storage engines”. He referenced the arrangement that enable IBM’s DB2 to act as an engine for MySQL on the the System i as a precedent.

Given that ScaleDB offers its proprietary storage engine for both MySQL Enterprise and MySQL Community without a commercial arrangement with Sun, the company will be hoping that its analysis is correct. However their remains a suspicion that the arrangement with IBM was enabled/complemented by a commercial arrangement.

Certainly, as this FAQ explains, the DB2 as a storage engine for MySQL is not necessarily the same as other MySQL storage engines, stating that “The source code for the IBMDB2I Storage Engine is available under a IBM ‘GPL compatible’ license. However, this storage engine acts as an ‘adapter’ that enables MySQL to talk to the DB2 for i DB2. It is not the source code for DB2 itself.”

Either way, the founders of the Open Database Alliance are not so sure that closed-source storage engines can be used with MariaDB. I asked Monty Widenius and Peter Zaitsev, CEO of Percona via email whether there was a chance that closed source MySQL storage engines could become part of the Open Database Alliance. Their responses:

Peter Zaitsev

“I think there is significant uncertainty about this one. It is unclear if MariaDB will be able to exist in close source version (via licensing fees to Sun/MySQL) or not. It is also not quite clear how GPL will work in this case - In theory with an open interface and plugin infrastructure it may be possible to distribute commercial storage engines (separately from MariaDB) and let users use them with GPL servers same as commercial drivers are used with a Linux Kernel.”

Monty Widenius

“This can only be done by buying MySQL licenses from Sun for each copy of MariaDB that is distributed.”

Which sounds pretty conclusive. With all respect to the expertise of all those mentioned above, it would appear that this issue is not going to be resolved without getting the lawyers involved. I’d be interested to know what the likes of Mark Radcliffe, Lawrence Rosen, and Eben Moglen make of it.