The deal – worth $360 million – is designed to help companies create Web content that can be accessed on devices other than just PCs, such as set-top boxes and PDAs. The companies will offer combined products, including server authoring and playback software.
The merged company will keep the Macromedia name and be led by Rob Burgess, who is the existing chairman and chief executive officer at Macromedia.
The merger follows a deal between the companies last November, whereby Allaire forged a partnership with Macromedia to bundle its application server with Flash and built an integrated toolkit for developing content.
The combined company will work to bring Allaire's ColdFusion development platform into line with Sun Microsystem's J2EE standard.
Macromedia expects to close the deal by the second calendar-quarter this year. The company's shares closed up almost five per cent to $44 on Nasdaq.