CORRECTION, 2:40 p.m. PT: There has been clarification since this story broke. Adobe has not officially released the CS2 software for free. Instead, it has canceled its CS2 license management servers because of a technical glitch, so for those with existing licenses it is now offering downloads that do not require contact with the licensing servers. While Adobe admits this may be seen as it giving its software away for free, this service is intended for those with existing Adobe CS2 licenses.
Adobe's popular Creative Suite has been developed way beyond the capabilities of the initial versions of the software; however, older versions such as CS2 are still very powerful image-manipulation and content-creation tools. Still, they are no longer supported by the company and could cause problems or fail to run when installed on computers running the latest versions of OS X or Windows.
Nevertheless, if you have an older computer or have virtual-machine software configured with an older operating system compatible with CS2, then you should be able to get CS2 running. Unfortunately for Mac users, CS2 is a PowerPC application, so it will require the use of either an Intel Mac running OS X 10.4 through 10.6 with the Rosetta translator installed, or the use of an older PowerPC Mac.
The only versions of the OS X client that Apple supports in virtualization are those that do not include the Rosetta translator (OS X 10.7 and higher) which is required for running older PowerPC code on an Intel-based Mac. Therefore, while you can either virtualize the Server versions of OS X 10.6 (which is rather expensive and no longer available) or earlier, or hack virtualization software to allow installation of the OS X 10.6 client, the best option for current Mac users is to perhaps configure a Windows XP virtual machine and install the Windows version of CS2.
The CS2 download requires you to first get an Adobe account and a CS2 license, then download the installer from the CS2 downloads page.
Since this release, the Adobe Web site has been flooded with activity, so you may have to either wait for it to come back online, or access the download links directly through the SlickDeals Web site (the previous link on this page direct-links to Adobe's servers).