EDIT: just forget what i wrote under this sentence, didnt understand the OPs post at first and thought he asked why bioware put lightsabers in game and not why the council had it.
"The first lightsabers came into being when Jedi combined advanced offworld technology with a forging ritual, learning how to "freeze" a laser beam. By the time of the Duinuogwuin Contention around 15,500 BBY, their studies and researches with this "frozen blaster" technology yielded success; they developed a method to generate a focused beam of energy that arced circumferentially back to its source, creating a controlled energy circuit and leading to the first portable high-energy blades."
"With Naga Sadow's invasion of the Republic in 5,000 BBY and the subsequent start of the Great Hyperspace War, the technological innovations pioneered by the Sith Empire were brought to the Republic and the Jedi. However, the majority of Sith forces held to the use of Sith swords, while the Jedi continued to use the protosabers, as they had not yet had time to adapt and implement these new designs. With the Sith defeat at the end of the war, modern lightsabers were adopted by the Jedi order. By 4,800 BBY they were almost universally utilized by Jedi."
shamefully taken from http://starwars.wikia.com/wiki/Lightsaber
btw we are playing about 3500 BBY (correct me if im wrong on this), so lightsabers were invented already and the theory was there for over 10000 years, thus explaining the holocrons with the data in it.