For anyone who's interested: I've managed to run OpenSesame (see below for the most recent version) from a USB-stick, using Portable Python 2.6 (EDIT: using WinPython 22.214.171.124 as of OpenSesame 0.27.2). It works really well, apart from being a tad slower than the original (as is to be expected, of course), but that seems largely due to the fact that OpenSesame is run from source. It has all the toolboxes built in, even the eyelink-functions.
I recommend that, if you would like to use OpenSesame Portable for experiments where timing is crucial, you test the timing on your specific system. If, after that, you would be so kind as to report your findings here, it would be greatly appreciated.
OpenSesame Portable is a nice solution when you're using different computers a lot, or if you want to have people fill out questionnaires at home or anywhere outside of the laboratory. Another great possibility is using it in education, so there's no need to install OpenSesame on a lot of computers (which might prove to be a bit of a bother, considering the IT departments of some universities).
|OpenSesame 0.27.2 (Python 2.7)|
|WinPython-OpenSesame-0.27.2 (Python 2.7)|
For downloading, see here and select the version of your choice.