Exactly my point... has anyone written this yet? I am desperate to use DNN but refuse to pay MS prices.

Bret,

you are welcome to create a MySQL data provider for DotNetNuke - for core and some of the packaged module, it shall take ony a few months for an experienced MySQL developer. As Scott stated before, DNN supports the use of different databases - but the only available provider atm is a commrecial Oracle provider and attempts to create MySQL and Firebird did not succeed - and you will need a dataprovider for any module you want to use...

Said this, I suggest to use free Microsoft SQL Server 2005/2008 Express, which is fine for small and medium sized web sites and supports all features needed for DotNetNuke. It supports Databases up to 4GB GB and is limited to a single CPU and 1 GB RAM, which shall be fine for most web sites, see www.microsoft.com/SQL (and IMHO the availablility of this free product leveraged the need for any additional data provider). you will, however, have to take care to backup your database, due to SQL Server Express does not include the feature of scheduled backups (there are free solutions available). Make sure to download SQL Server 2008 Advanced Edition, which includes Management Studio, Reporting services and Fulltext Indexing as well. you need to download and apply SP1 separately atm.