Manga creator Shuho Sato has been experimenting with different ways to actually make money with manga, which is a harder puzzle than you might think. The problem is that manga creators usually break even or lose money on the serials that appear in Japan's weekly or monthly anthology magazines; they make their money when the collected editions (tankoubon) are released, but that doesn't always happen, so it's a gamble. Sato has written some sharp commentary about the economics of being a manga creator, and he pulled his series Give My Regards to Black Jack (also known as Say Hello to Black Jack) from his print publisher, Kodansha, and he had previously put it up online, which was at least initially a financial success.
Now the Finnish digital comics publisher Amimaru is publishing Give My Regards to Black Jack in English on its Facebook app, which is in open beta. The price is 12 Facebook credits, but starting Sept. 15, it will be free, per Sato's request. Sato is also making the series available without restriction for "second uses" such as novelizations, and has said he will stop enforcing his copyright for an indefinite period.
How does he make money this way? It's possible that Sato just doesn't care, as he made it clear when he parted company with Kodansha that he was not satisfied with them. It's worth noting that his newer series, New Say Hello to Black Jack, was published by Shogakukan, and he's not giving that away for free, so presumably he figures he has made all he can from the first series and it's a better use of his time to use it as a promotion than to try to eke a trickle of royalties from it.