Most recent beta is damaged.
Hi Ben this is a problem for 10.10 and 10.9.5 it is already fixed in the next BETA
the next beta should work on 10.10 again. Apple did change the sign-process for 10.10 and the upcoming 10.9.5 release.
Thanks for the report, and again sorry for the lag. Not easy to find the "needs moderation"-posts.
With best regards,
Hi Ben - please can you confirm that the latest BETA is working for you on 10.10