When the FlexWiki administrative staff deems that a stable and useful point has been reached in the codebase, they grab an interim build from the BuildSystem and post it to the SourceForge download site. This means that officially released builds are identical with one of the BuildSystem builds. However, no support is available for interim builds, so installing from the BuildSystem site is strongly discouraged unless you want to do all your own support. Additionally, the SourceForge site provides us with a high-bandwidth, mirrored download system, so it's faster to download from there!