Here is a download link to this patch.
If anything, it is useful for playing the Nemesis Challenge on a Mac, since Nicalis has no plans to update the Mac version. The only way to actually play it in this version of the patch is by editing mods.txt and setting them to "unlocked", which mods.txt itself conveniently explains how to do. This works for Curly Story and the other Challenges as well.
As it turns out, Cave Story+ for Windows and Cave Story+ for Mac really aren't all that different; all the data for the Mac version is in the same "data" folder as the Windows version, but "data" is found within "resources", which is found within another folder which is the root of the contents of Cave Story+.app. These parent folders are what makes Cave Story+ compatible with Mac, and there is also a CodeResources file that makes the whole thing work together, similar to CS.exe, which is the Windows executable for Cave Story+.
As far as the rest of the Cave Story+ patch goes, everything seems to be pretty normal, except the Remastered soundtrack does not work. Sometimes when going through the Music selector in the Options menu, Cave Story+ crashes, and sometimes it just goes to "New". This is because the CodeResources file in the compatibility folder does not utilize it. The reason it didn't work even after I patched it is because this file was not in the Windows version and so I could not make it part of the patch. If equivalent code exists, it probably exists within CS+.exe. If you could find out what code they use in CS+.exe it could be a breeze for someone who actually knows a thing or two about modding.
I also do not know what the deal is with the Xmas thing. I don't know much about it so I don't know whether it is working or not, and if not, how to get it to work. Maybe you could put some Xmas-related code from CS+.exe into the CodeResources but I don't know.
As not everything in this patch works correctly, it is incomplete. I need a real modder's help to edit CodeResources so that the other new stuff will work.
EDIT 3/11/12: It turns out that obtaining the Nemesis will not unlock the Nemesis Challenge. I think it's that the game won't understand the code in mods.txt that unlocks things based on whether you've obtained a weapon, unless the CodeResources is updated. Right now the only way to unlock the Nemesis Challenge is by setting it to unlocked in mods.txt.
Edited by TorchicBlaziken, 11 March 2012 - 09:31 PM.