lilydev-3.0.iso -- not mounting on mac osx

[Paul Morris]

Hi all,  On mac osx 10.10.2 I get the following when trying to install LilyDev 
3:
_______________________
Warning
The following disk images couldn’t be opened
Image
  lilydev-3.0.iso 
Reason
  no mountable file systems
_______________________

…after downloading from here:
http://www.et.byu.edu/~sorensen/lilydev-3.0.iso 
<http://www.et.byu.edu/~sorensen/lilydev-3.0.iso>

...as linked from here:
http://lilypond.org/doc/v2.19/Documentation/contributor/lilydev 
<http://lilypond.org/doc/v2.19/Documentation/contributor/lilydev>

Has anyone else had this problem?

Thanks,
-Paul