TheBrain 32-bit (Mac OS 10.5-10.9) will work with OSX 10.10 Yosemite but you will be prompted, when first loading TheBrain, with this message:
Click More Info...
This will bring you to a web page to download Java 6 for OSX. Download and install this and TheBrain will then load.
The direct link for the Java SE 6 runtime download is: http://support.apple.com/kb/DL1572?viewlocale=en_US&locale=en_US
TheBrain for 64-bit (Java 8, Yosemite, etc.):
If you are running TheBrain for 64-bit and you see this error:
you do not have Java 8 installed, which is required on Yosemite. Please visit www.java.com/download to download and install Java for Mac.