The purchase will further consolidate the market after Autonomy bought Interwoven, Vignette's WCM rival, earlier this year.
Vignette shareholders will receive $8 (£5.30) per share in cash, plus 0.1447 of an Open Text common share for every Vignette common share. This equated to approximately $12.70 (£8.42) at market close on 5 May, according to Open Text.
"The combination of Vignette with Open Text will extend the breadth of our offerings, and further Open Text's position as the leading independent ECM vendor in the marketplace," said Open Text chief executive and president John Shackleton.
"Vignette's customers represent some of the world's most powerful online brands, and we are excited about the opportunity to expand the relationship with these customers and partners."
The transaction is expected to close in the second half of 2009.
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