What is the relationship between libfilezilla and FileZilla?

libfilezilla has been started by moving core functionality out of FileZilla (the client) into the new library, so that this functionality can be used in other programs as well, e.g. FileZilla Server.

Since FileZilla is an FTP client, can I transfer files using libfilezilla?

Short answer: No

Long answer: Not yet. libfilezilla is still in development and so far only few functionality has been moved from FileZilla into libfilezilla. Cleanup of application specific code, turning it into a general-purpose library takes a lot of effort. It takes time, but in future versions additional functionality will be added to libfilezilla.

My program already uses wxWidgets/Qt/Boost/etc..., can I still use libfilezilla?

Yes. All of libfilezilla lives in its own namespace, so it should not clash with any other library you are using. By overloading some functions and specializing some templates you can easily integrate libfilezilla with your other libraries. See for example <libfilezilla/glue/wx.hpp> how to combine libfilezilla with the wxWidgets library.