TurboTax Business is a different program from the personal program which comes in Deluxe, Premier, and Home&Business versions. The business program is only available as a CD or download and only for PC, not online and not for Mac.
You may be able to run Windows on your Mac using Boot Camp or Parallels, or you may just want to buy a cheap PC for your business taxes, if you want to use TurboTax.
Incidentally, the form 1065 return is due March 15, not April 15, and the late penalty is $195 per person per partner.
If you have a single-member LLC, and you have not filed a special form with the IRS, then you are treated as a disregarded entity and would file a schedule C as part of your personal tax return, not a form 1065. Form 1065 is only needed if the LLC has more than one owner.
