The Portable GIMP is a free and open source GIMP viewer for the Mac and Windows operating systems. Although it was made to be compatible with both platforms, it can only be downloaded on the Mac operating system. It's not very often that a free software has some kind of limitation like this, but it's very likely that the company who made the software has taken it upon themselves to try and be able to distribute their program across multiple platforms. For those who are wondering why they can't download the software on Windows, there are some very good reasons.
Firstly, they are simply trying to be able to get it out to the public so that they can promote it as being free and open source. The fact is that it's not really true, since the application is actually technically not free. Since it is open source and has been made available for free download, it would be extremely dishonest if they said that they could distribute it in a free format. They are also actively trying to find ways to try and get people to pay for their application in the hopes that they will make more money from this effort.
Therefore, since this is an application that has been made available for free software download on the Internet, the fact that they made it run on both Windows and Mac operating systems is purely a marketing gimmick. The only thing that could possibly justify such a limitation is that it's meant to be used to promote the idea of being able to run it on a variety of platforms. In truth, the application is only meant to be run on one platform, which is Mac. So, if you're looking for the Portable GIMP for Windows, there is really nothing to worry about.
