When I reviewed the app, my copy of Excel 2010 threw up a number of messages about security cards, and certificates and so on. Eventually, it seemed to settle down and work properly. My advice here is to keep trying; enable the macros and so on, install the certificate when it throws that up (this is quite safe to do...well, none of the security programs on my machine are objecting and they are in good working order), and so on.
It's definitely worth the effort; it's an amazing app.
But yes, it would be nice if the app was available to everyone on all platforms.
Hmmmmm....I wonder if this could be done as an online app using PHP and MySQL??
The images would be a problem...hmmm...been a while since I did any serious PHP programming. Too busy with online gaming.