Reading the article, Jeff Goldblum's famous line from the movie Jurassic Park ran through my mind: "Life finds a way." Actually, that whole movie is a commentary on this article. The combination of human hubris and the persistent ability of living things to survive and thrive is a deadly combination when it comes to virulent diseases.
I have read about some of the things mentioned in the article, such as the 1977 H1N1 influenza release and the SARS incident, so I think the article is credible. Certain famous incidents such as the release of anthrax in Sverdlovsk, Soviet Union in 1979 that killed at least 100 people was not mentioned, though, so not a complete history of all the biggest releases.
The same researchers today who have created doomsday strains of H5N1 influenza virus are probably just as confident as the scientists in the past that they can keep their creations safely ensconced in their labs. Now that the deadliest strain of Ebola, the Zaire strain, is currently terrorizing West Africa for the first time, it's a good reminder of what happens when a deadly pathogen runs loose in a population.