Traditional india ink was often just lamp-black (carbon) mixed into gelatine and water. It behaves fairly similar to blood, with problems of globs, dry tip; you just learn how to work with this until it's second nature. Sorta like how gel-ink pens refuse to write unless the pen is held at just the right angle (which, I think partly because of my weird lefty grip, I've yet to figure out). Blood seems to flow a bit better using natural quills as opposed to metal nibs. So long as you dip the pen in alcohol or diluted acetone and blot it dry, on ocassion, it's really not too bad to write in. If you really wanted non-coagulating ink, you could always add coumadin. Just don't eat it or you might, ya know, die.
The problem with blood is that over time, it deteriorates until only the tiny traces of iron from the hemoglobin remain visible. This can be pretty difficult to read.
Oak gall ink is lots of fun. It's neat to see it change color as it cures.
I'm not quite as quick to call bullshit on this claim as I am with the articles claiming to solve the energy crisis. I spent four years writing code for modules that interacted directly with bastations, but without even a taste of a technical explaination why there is something wrong with the amplifier, it's a coinflip.
I wish this sort of journalism came with citations, so I could no for certain whether the author is dumbing things down to avoid scaring away the non-technical audience, or because they are lazy bastards who copy-pasted a press release without bothering to investigate if there was any validity to the claims.