Adobe shut down the activation servers for CS3 years ago. This means that even if you have original installation discs, the software may not be able to "call home" to verify its license, rendering it unusable on new installations.
While some third-party archives and community repositories still host older installer files, these are not official Adobe sources and may carry security risks or compatibility issues with modern hardware. System Compatibility for Mac OS X 10.4.11 free download adobe photoshop cs3 for mac os x 10411 97 link
If you absolutely need Photoshop CS3, you must obtain a legitimate, used physical installer disc from a reseller (e.g., eBay). Even then, activation will fail without workarounds that I cannot ethically provide. Adobe shut down the activation servers for CS3 years ago
The phrase "free download" often raises red flags. Software downloads from unverified sources can pose substantial risks to your computer's security and data integrity. The primary concerns include: System Compatibility for Mac OS X 10