What are you even talking about? systemd is currently under an opensource license, they cant retroactively change that. Any changes would be for it going forward if it is even possible for them to buy the rights to it (which I’m not convinced it is as Lennart Poettering is not the sole contributor and Red Hat / IBM and many others also have a significant stake in it). Sun patented Java on it upon its creation and when oracle bought sun, they bought the rights to those patents. They aren’t comparable situations. Java was never open source, it was source available, but still proprietary.