The Order of Sith Pirates was founded by Darth Slayer in 4 BBY. This was an organization of Sith who lived only for profit. The Sith Of this order were not truly masters of The Dark Side. Darth Slayer having only learned the Dark Side from a Holocron, was unable to impart his followers with a true understanding of the Dark Side.
In 2 ABY after the Death Of Darth Slayer the organization dissolved. 8 Years later however, in 10 ABY the order was restored under the leadership of Darth Scourger, Slayer's old Apprentice. Despite the efforts of the Sith This order never returned to the glory it had in the days of Darth Slayer, and dissolved permanently in 16 ABY.