For sure it is not the same but both are small real-time Operating systems.
Advantage uC-OS you can get a great documentation including the source code of the OS by buying the book written by Jean Labrosse. The OS is not the latest version.
embOS offer a little more driver options and supports different processor families.
They have similar licensing schems which is important if you want to use it in a professional application. Both are royalty free, that means you do not have to pay for each device you sell ;-)
Hope this helps a little, Bob