I have been running MAMP Pro 3.05 successfully in Yosemite up to DP4 on a partition that was a clean install of Yosemite.
I now have run the installer for DP5 over m
Just found workaround from MAMP on Twitter
Workaround for the 10.10 Preview 5 bug: Rename the file “envvars” located in into “_envvars”