The Department of Justice closed its investigation into the proposed merger between ACI Worldwide Inc. and S1 Corp., the companies announced Friday.

The Justice Department had delayed its ruling since early October, when ACI, of New York, agreed to buy S1, of Norcross, Ga., for $360 million and 5.8 million ACI shares.

The decision brings to an end a long saga that began in the summer when ACI made a hostile bid for S1, which was then in merger talks with Fundtech Ltd. (now Fundtech Inc.). The bid disrupted that merger, and Fundtech ultimately merged with software provider Bankserv, owned by GTCR LLC, a Chicago private equity firm, in a deal valued at nearly $400 million.

Under terms of the agreement with ACI, S1 stockholders will get $10.00 in cash or 0.3148 shares of ACI stock for every S1 share they own, subject to proration. In total, 33.8% of S1 shares will be exchanged for ACI shares, and about 66% will be exchanged for cash. The deal had been subject to various conditions, including the termination of the waiting period under the Hart-Scott-Rodino Antitrust Improvements Act.

The closing of the investigation will provide clarity to the customers of both ACI and S1, says Christine Barry, a research director for Aite Group.

Customers will now have access to "the best of breed of both solutions, which are two of the top cash management solutions in the market," Barry says, adding that ACI will be "a strong force in the industry."