According to the FileZilla FAQ:
FileZilla is free open-source software distributed under the terms of the GNU General Public License free of charge.
Basically this means that everyone, including corporate entities, can use FileZilla, including but not limited to private, educational and commercial use.
When you install it you have to opt out of at least one, if not two, bundling offers. While many installers provide you the opportunity to install a bundled offer, I really think that if you are releasing the software as open-source under the GPL, then you should embrace the spirit of the license and make the included bundles opt-in. And why you are at it, maybe you could add a section to the FAQ on what the funds for the bundles and the website sponsors are used for.