I am portableapps.com user since many years. I am using locally on my computer and on my USB drives Skype, LibreOffice, Java, OpenOffice, Google Chrome, Firefox, VLC, 7Zip, TeamViewer, GIMP, Eclipse(for now this is on development progres), Opera Browser, Pidgin, Foxit Reader... Totally about 40 applications.
Portableapps.com make portable apps of open-source and non closed-source applcaitions. They have ISO certificated format which is open source. It is simply and stable.
It is possible to update the portable application automatically if the user use also portableapps.com platform which is also portable and very easy to use and small.
Also it is possible to solve file association with simply other portable apps which are writed by portableapps.com developers.
Also the format bring with it other features. For example: each portable app directory must contain a Data directory which includes all personel preferences files (user-data files, same as "home" directory on Linux). For example if you remove this folder, the portable app starts like first time. You can see all preferences files inside on it easily.
Please make a portable version under portableapps.com format.
Thanks in advance