GIMP Portable 2.10.34 could be downloaded from the developer's website when we last checked. We cannot confirm if there is a free download of this software available. This free program is a product of PortableApps.com.
The following versions: 2.8 and 2.1 are the most frequently downloaded ones by the program users. GIMP Portable is included in Photo & Graphics Tools. The GIMP Portable installer is commonly called GIMP.exe or GIMPPortable.exe etc. According to the results of the Google Safe Browsing check, the developer's site is safe. Despite this, we recommend checking the downloaded files with any free antivirus software.
From the developer:
GIMP Portable is the popular GIMP for Windows image editor packaged as a portable app, so you can take your images with you and do your editing on the go. The program can be used as a simple paint program, an expert quality photo retouching program, an online batch processing system, a mass production image renderer, an image format converter, etc.
You may want to check out more software, such as GIMP, Extension Installer for Photoshop + GIMP or GimPad, which might be similar to GIMP Portable.