Hello kinorsi,
As seen in the "Java Service Task" section in "8. BPMN 2.0 Constructs" of the user guide, $ represents a "Delegate Expression" and is used to refer to a (Spring) bean implementation class that is configured in the configuration file of Activiti.
#, on the other hand, represents an activiti:expression (either a UEL method expression OR a UEL value expression) and is used to refer to a "named object or bean" usually present in the execution context's process variables.
Reading the "Expressions" section in "Chapter 4. The Activiti API" of the user guide should give better details regarding UEL expressions in Activiti.
-
A M Bharath