Apple - truecrypt 7.1a requires Mac OS X 10.4 or later on Yosemite 10.10
- Copy the mpkg from inside the downloaded disk image onto your Desktop.
- Right click the mpkg file and choose Show Package Contents, then open the Contents folder.
- Open distribution.dist with a text editor.
Remove lines 13 to 18.
Save the file and open the mpkg normally.