There is the dali-interface Python library which seems to support a few PC DALI interfaces based on USB-HID and serial. I don’t know how well the translation between USB-HID/serial and DALI is standardized, so I can’t tell you how compatible this library is with DALI interfaces that are not explicitly listed in the README.

Software using this library includes dali_mon for monitoring the DALI bus and dali_cli for sending commands.

Sure, but the newest version of each package is four years old and riddled with dozens of Debian-specific patches that somehow only make it run worse.

To my knowledge, there has been some discussion regarding the AGPL as to whether using software through a network even creates the kind of legal relationship between provider and client such that the client has standing to request the source code. I assume similar discussions would crop up regarding the SOWPL.