Hi Marc,
welcome to the forum and thanks for taking the time to post!
I may have some good news for you. If you are looking to send billFLO invoices we have browser based versions of billFLO seller which are mac compatible. (You can see a video of billFLO seller in action here >>
http://www.billflo.com/seller_faq.php)
billFLO buyer, for receiving and importing invoices, is PC based currently. A mac version is on the roadmap but not imminent.
Does that answer your question?
Ian