The Internet Archive often hosts "abandonware" ISO files of original installation discs. While still technically unofficial, these are generally safer than random download links on file-sharing blogs. Final Verdict
If you are looking for a portable download link because you need a simple web editor, you might be better served by modern, safer, and free alternatives: microsoft frontpage 2003 portable download link
Here is a comprehensive look at the state of FrontPage 2003 in the modern era, why people still look for it, and the safest ways to handle legacy web design. Microsoft FrontPage 2003: The Legacy of WYSIWYG Web Design The Internet Archive often hosts "abandonware" ISO files
A "portable" application is a version of software designed to run without an installation process. Traditionally, FrontPage required a full Microsoft Office installation, which modified system registries and occupied significant disk space. A portable version theoretically allows you to run the program directly from a USB drive or a single folder on your desktop. The Risks of Downloading "Portable" Legacy Software Microsoft FrontPage 2003: The Legacy of WYSIWYG Web