JOHNNIE WALKER  jazzyguy: The import function isn't for importing games, it's for importing user info about games & collections. This is the same as iTunes' import functions.

What you need to do is:

a) Download MAME OS X, then open the MAME Library preferences & tell MAME Library where MAME OS X is.

b) Again in the MAME Library preferences, tell MAME Library where your ROMs folder is located.

c) Choose the 'File < Update Games from MAME OS X'.

MAME Library will be able to you a list of the available games, and let you launch those games.  
(Version 0.6.1)

JOHNNIE WALKER  I had indeed overlooked bumping the version number for 1.5b3.

'Luckily' there was another bug which needed a quick fix, so we're already up to 1.5b4, this time with the correct version number!  
(Version 1.5b3)