The CP210x (e.g. CP2105) datasheets mention “Royalty-free" VCP and USBXpress drivers. What does this mean? Are these drivers open source?
"Royalty free" means VCP and USBXpress drivers can be used and distributed at no cost. Silicon Labs collects no fees for driver usage and distribution.
Furthermore, these drivers are not open source, and they only support Silicon Labs devices.
Win7 ships with the correct 'winusb.sys' file, but is missing an updated '.inf' file that associates the driver with "usb\ms_comp_winusb" devices. Normally if the USB device supports Microsoft OS descriptors, then it will allow Windows to automatically install the WinUSB driver. This mechanism is supported "in-box" for Win8 and newer. For Win7 the mechanism is supported through Windows update. Depending on the update policy for the Win7 machine, the appropriate driver may or may not be already available on the machine. If it is not already on the machine, user can use the following manual procedure to install the driver if necessary.
5. Navigate to the temporary folder with the downloaded driver and complete the installation.
This procedure only needs to be done once.