FrontBase is now available for free. Please see the FrontBase website  for details.
A first experience with FrontBase, WO 5.3.1 and MacOSX 10.4.6
Make sure you have the FrontBase jdbc connector accessible from your WebObjects applications. I placed mine in /Library/Java/Extensions/ Make sure that the FrontBasePlugIn.framework is located in /Library/Java/Frameworks Make sure that you have added the framework to your project or you will not be able to establish a connection to your database, even though you'll be able to see your database from EOModeler. If you haven't yet assigned a User/Password combination to your database, you still must include User information in order for the connection to be established. Use _system to get started. The URL for basic connection is: jdbc:FrontBase://localhost/my_database_name
The documentation available at the Frontbase site is very complete. The only gotcha was that I was left with the impression the framework was only necessary for WebObjects 4.5 and below. This is not the case, you have to install and include it for WO 5 projects too.
Migration from MySQL
In most cases the datatypes are exactly the same. Here are the FrontBase equivalents for common datatypes in MySQL that are different:
TEXT --> CLOB
DATETIME --> TIMESTAMP
INT --> INTEGER
MEDIUMBLOB --> BLOB