MnMWizard :
I think the program just pays you for hours of time running the program, so multiple instances would probably increase pay rate by a lot.
From what I understand of this program, a remote server contacts your computer and then uses it to access web pages. Leaving aside the security implications of this, the mode of operation would mean that it could only contact a single instance of the program running on your computer (unless you had multiple connections to the Internet). I believe it pays you for the amount of work done rather than the time spent using it, so multiple instances would offer no advantage even if it could be done.
I said "Leaving aside...", but I'm not sure that you should. Do you really want a program running on your computer, contacting the Internet and you don't know what it's doing? It could be testing web sites; it could be sending out Spam, it could be sending your bank details to the remote server.
Some other aspects to consider: 1.) Your ISP might look upon this as commercial use, which probably isn't allowed by the terms of your contract. 2). Users report that this program randomly minimizes what is on your desktop - often in the middle of games. 3). As already said, it probably costs almost as much, if not more, for the additional electricity used as you would earn.
If none of that discourages you then go ahead - but forget the idea of running multiple instances of the program.