That "for free" link isn't accurate at all, it claims you have to compile Deskflow yourself, but on Deskflow's Github they offer binary releases.

I don't remember why Barrier was forked from Deskflow, but I've been using Barrier for many many years now. Now that I think of it, I do notice bugs, that maybe I should try out a new version to see if there are life improvements. E.g. with keyboard layouts, even when both systems are running Windows, the target system can be confused what character it should be outputing; and I need to hit "reload" to reconnect after returning one or both systems from standby, sometimes clipboard sharing also breaks.