Note: for now, only CH579 supported.
There are no LICENSE section or files provided by WCH, however this SDK itself can be downloaded from WCH.cn without reading some EULAs or agree to one of them. Consider they are provided AS-IS and without warranty. These files will be deleted if they file a DMCA request on this repo.
Also, part of this repository uses some open source softwares without proper licensing (they even removed LICENSE headers from paho.mqtt.embedded-c library files), so use this at your own risks.