About Open Transactions
I think that Open Transactions is a much broader concept than my payment system. It seems to have more features, but having more features also has a disadvantage: if it also makes the software more complex, this makes it more difficult to have the source code reviewed by independent parties. I believe that having independent code reviews, and hence having clear, simple, publicly available source code are very important for building trust in software.
Maybe OT solves certain problems in a different way than the concept described by me. In that case: please point me to the disadvantages / flaws in my approach, and explain me how to do better.
Maybe OT can solve certain problems in the same way as I do. In other words: maybe my concepts can be implemented on top of OT. Even if that is the case, I will initially not use OT, for the sake of simplicity (see above reasoning). However, I will make the software layered in such a way that the top-level layer can easily be re-used on top of another bottom-layer. For instance, if an implementation on top of OT turns out to be a popular request from the community, I might decide to add that, or to switch to OT in the future.
FYI, I just posted a video walkthru of OT, which will probably help you a lot in understanding the concepts, and what it actually does.
Check it out here: http://vimeo.com/28141679