I haven’t been able to get official word on how this came about, but Phase One is now offering Capture One Express (for Sony) free on their Web site. Apparently developed in cooperation with Sony, this new Capture One Express 8 version is complete.
What you don’t get (requires updating to Pro version) are tethered capture, camera live view, sessions, focus mask, local adjustments, repair layers, film grain, skin tone editor, CYMK support, image output recipes, soft proofing, customizable interface, multiple monitor support, scripting (on Mac), templates, and keystone correction. While that seems like a long list, the list of usable features is very extensive.
All Sony mirrorless cameras currently available or available in the past are supported by this converter. Note that if you have another version of Capture One version 8, the file name of Capture One Express for Sony is the same and you have to be careful not to install over the other file (e.g. drop and drop the application to the Applications folder on the Macintosh). Indeed, on my Mac, the size of the file and version number are the same.