This week's book giveaway is in the Testing forum. We're giving away four copies of The Way of the Web Tester: A Beginner's Guide to Automating Tests and have Jonathan Rasmusson on-line! See this thread for details.
I just have downloaded the JForum 2.1.8 Source Code to have a look and I have not seen the spanish language propertie file.
I am not sure if that file does not exist in the project or if it's a target for the next version.