How can I upload Modified firmware/ software on a mac

Wow I am the only mac user here? crazy.

You can pick up an old laptop on ebay for 50 bucks yhat is more thsn enough to run the stock host.

For this printer the firmware is not on the SD card. That file that is on there is something entirely different and no one really knows what it is since it is encrypted. The firmware is actually burned into the processor on the controller. You can user Adruino IDE if there is a MAC version. I would suggest looking into changing the firmware. There is a thread here and one on Voltivo's forum. Once you see what needs to be done check for MAC alternatives.

It may actually be easier on Mac or any other Unix environment as you don't need to worry about any extra device drivers and such.

I used luc's firmware as mentioned above: github.com/luc-github/Repetier-Firmware-0.92

I also have updated the doc a bit to be more descriptive and verbose.  I did the full setup on my macbook pro with no problems.  If you run into any gotchas or simply want to help out feel free to fork luc's repo and submit a pull request with your fixes.

Ok, hears what I did on my mac. First I downloaded luc's 0.92 Repertere (I presume you have already done that as you said that you opened the .ino file). Then you replace the variants.cpp and USBcore.cpp files in your arduino program with the ones supplied by luc (src folder contains them). Now to replace the files go to your applications folder, right click on  arduino executable and choose Show Package Contents. Look for the files mentioned above (use search if you have to) and then replace them with the ones you downloaded.
Now open the .ino file. If you are running da vinci 1.0 you do not need to change anything otherwise read luc's instructions about da vinci 2.0 etc.
After you juper your printer to the fallowing:
Under the tools menu select the board type as Arduino DUE (Native USB Port) and the proper port you have connected to the printer. The port should show up as USB...... like you mentioned in your post. Now you can try to compile the firmware to check there are no errors (this will only compile, you do not have to upload in right away if you do not want to). To just compile, click verify (button right at the left corner in arduino). If no errors show and sketch compiles (reporter.ino) then, with the printer jumpered (no software installed) you can upload the firmware (button next to verify). It will compile again and you can fallow the upload progress below.
Once flash is done do not forget to send G-Code M502 then M500 from repetier's Print Panel tab or from the printer menu "Settings/Load Fail-Safe" and accept to save the new eeprom settings.
At this point, you should have Reperter up and running in your printer, switch it on and off (it's sometimes necessary). To connect to your printer and to calibrate it, you need to configure Repertere host. I used setting found in hear (http://voltivo.com/forum/davinci-firmwa … figuration). You can start with those and modify if necessary. After you successfully connect to your printer using Repertere Host (xyzware is now useless) you should calibrate it. Consult the reporter host manual if necessery but it should be easy enough to figure out. To calibrate you need to heat up the bed and extruder, home axis and use the paper method (it has been described many times in this forum). After that is done you are ready to run your first print job. You need to have slice3r installed for it to work from within reporter host (and configured). Before you hit "run job" though, you should heat up the bed and extruder to the required temperatures manually from the print panel in reporter host.
Hope this helps, if something was left unclear however, just ask.

I have a question about the jumpers: on this and other forums I've seen, the J1 jumpers appear to be fairly simple to connect to. On my machine (picture attached) the left hole has no contact point. Is there a way around pulling the whole board out to solder a contact point? more detailed image at metrob.us/IMG_0005.jpg

There's a version that supposedly works with Duos. Link is github.com/luc-github/Repetier-Firmware-0.92

This is kind of the problem - I only have one pad. The left hole is empty, no solder just a hole in the motherboard. There's really nothing conductive around the hole.

You are correct, and I was able to close the circuit and wipe the firmware. I've now successfully uploaded the repetier firmware, it's working well with Simplify3d and Repeater Host on my mac.

Unfortunately, now I have other issues - haven't been able to get a single print to stick since switching to Repeater firmware, even though I'm using the exact process as before. Need to spend some time dialing in the temps I guess.