When you buy it it is programmed with a code generated by your computer (you generate this and give it to the company before they send you the software). This means it can only be used on your computer, I think. When I tried to use my copy on a work computer I received a message along the lines of "This software is not licensed for this computer blah blah".
There may be ways round this. But I'd suggest you buy it as it is a great help... not quite sure where I stand in terms of morals and principal on this one though - it certainly gives you an advantage that you're not supposed to have.