How can I declare temporary variables? Are Smalltalk-80 pipes "|" not supported?
You cannot declare temporary variables in a block. This is a limitation we plan to tackle soon. In a shell, if you want to declare a globally variable, then use the Var class (cf Scripting Section).

Why when I lunch the Athena Shell I have a owl: as a prompt. I would expect athena:
The rational for having owl probably root in the ancient Greek Mythology. Athena was attended by an owl.

How Athena differ from SmallWorld, the work done by Tim Budd?
Athena is built on SmallWorld. It means that most of the interpreter in Athena is SmallWorld's.
Interaction with Java and hability to be scripted represent the major difference from SmallWorld. In term of lines of code interpreter of Athena is 1275 lines of code, whereas most of it was written by Tim (except the method lookup, a dozen of VM primitives). Athena is 2748 lines of code long. More than half of Athena does not inherit from SmallWorld.