Microsoft and Time Warner, both giants in their respective fields, announced in April that they, together with ContentGuard, had purchased most of the stake held in the firm by its original owner, Xerox.
ContentGuard is a leading provider of DRM technology, which controls how copyrighted digital content, such as DVDs or software, can be viewed, used, or abused.
Microsoft already held a stake in the firm, and commentators saw its increased holding in the company as a sign that Microsoft was keen to gain a share of the digital music and movie market.
As both Microsoft and Time Warner are industry leaders, the joint acquisition requires approval from EU competition regulators. The decision had been expected on Monday.