HPLIP is free, open source software, distributed under the following open source licenses:
Within the header of each source file, the license is listed which pertains to that particular piece of open source code. We suggest you view these header areas for further information.
Binary plug-in information
A small subset of HP devices require proprietary software technologies to allow full access to printer features and performance. These technologies cannot be open sourced. Because of this, HP is releasing binary plug-ins for each of these printers that work in conjunction with our Linux Open Source Printing Software to improve the printing experience for HP’s Linux Printing Customers. These binary plug-ins require the user to read and agree to a license agreement at the time of driver installation.
You can go here for more information about the Binary plug-in.