BusAcc X 5.1 for Mac was available as a free download on our application library. The application lies within Business Tools, more precisely General. The actual developer of this software for Mac is www.elsoldata.com.
From the developer:
BusAcc X is a FileMaker runtime application solution that doesn't need FileMaker to run and it is available for OS X 10.6 or later, or Windows XP or later.
You may want to check out more Mac applications, such as Dynadot Account Management Client, which might be related to BusAcc X.