This is intentional. The installer does not install any spyware and clearly offers you a choice whether to install the offered software. If you need an unbundled installer, you can still download it from http://download.filezilla-project.org/
Site Admin, FileZilla Project Forum - 4th July 2013
FileZilla still uses SourceForge, but appears to no longer offer the modified downloader which attempted to install.
It appears that +SourceForge took over the control of the 'GIMP for Windows' account and is now distributing an ads-enabled installer of GIMP. They also locked out original owner of the account, Jernej Simončič, who has been building the Windows versions of GIMP for our project for years. So far they haven't replied to provide explanations. Therefore, we remind you again that GIMP only provides builds for WIndows via its official Downloads page.