During the later part of 2011, the first push for multi-database support was made for the CMS, with a team from Hooduku implementing support for Microsoft's SQL Server (and inherently, the Windows SQL Azure Database). With the release of 2.5 in January 2012, the CMS was officially supported for the first time on a non-MySQL driven database. This support expanded with the release of 3.0 when PostgreSQL support was added.
The Joomla CMS continues to support MySQL, PostgreSQL, and SQL Server, but there are areas that need to be improved upon. If you browse the CMS Issue Tracker, you'll find that there are several reports of issues with these environments with the root issue being how the queries are formed in the code.
How Can I Help?
If you have access to a SQL Server or PostgreSQL environment, or are able to set one up (many *AMP software packages used for local development already support PostgreSQL, you just need to install the database server separately), we can use your help! We need people willing to install the CMS in these environments and use it as usual, noting any database related errors they may find. If you're able, we need to fix these queries or PHP methods, or in some less common instances, alter the database schema to allow these tasks to complete properly, while still functioning in all three supported database environments.
Sign Me Up!
If this interests you, I can be contacted via e-mail at michael.babker [AT] joomla [DOT] org. Help us help the millions of users of the Joomla CMS and improve our code along the way.