PortableApps' page on ZSoft Uninstaller portable
License: Freeware (Personal and Business)
but it looks like it's only for NON-commercial use, as explained in ZSoft's forum post on "License"
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The following license is presented when you install the product:
Copyright (C) 2004-2007 ZSoft
This license applies to everything in the package, except where otherwise noted.
This software is provided 'as-is', without any express or implied warranty. In no event will the authors be held liable for any damages arising from the use of this software.
Permission is granted to use this software for non-commercial purpose only.
So, basically freeware, only for non-commercial purposes though.
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I tried installing the NON-portable version and that's exactly what its license says (except that the Copyright dates have been extended through 2010).