The WordPress hosted app previously available on Sourceforge has been turned off. Fortunately you can still extract the data and install wordpress in your project area. I have done this for both my profile project and for MAF. There is a helpful blog on how to do it at http://sourceforge.net/p/forge/community-docs/Migrating%20WP%20from%20Hosted%20Apps/, though it only explains how to migrate project related blogs, not user related blogs. If you want to do the latter and are unable to puzzle this out, send me a message and I will do my best to help.