Well, MoM is portable. It consists of single exe file [mathomir.exe]. You can just copy this exe file anywhere you want and run it from there. If you use Mom in non-english language, then you should also copy the language.csv file into the same folder where you put the .exe file.
I like portable applications. Not because I need much portability, but because I hate large complicated software.
But, I was thinking, is Math-o-mir really really portable? Unfortunately, not to the extend I would like. The MoM has the keyboard issue. If you try to use it from another computer (one that you are not used to), you will not be able to do much math typing because the keyboard will not have the exact key placement you are used to. Unfortunately, for math typing all keys matter, not just the QUERTY part. For math typing you need to use CTRL, ALT, number-keys, parentheses keys, special symbol keys… much more frequently than when you type a plain text. On a borrowed keyboard typing math is real pain.
There is one another thing I wanted to share… Mike Croucher published the new article for the “A month of math software” serial on his Walking Randmomly blog. He mentioned the Math-o-mir there. Thanks Mike… BTW, his blog is much read and is a relevant place for those who are interested in math.