Yes drools:taskName can be same in multiple process definition files as along as id is unique.
If you use Drools Guvnor, to define your process, then unique id is generated by default.
Sample Code:
<bpmn2:userTask id="_4AA55365-51C2-4763-A036-B29F7CB3388A" drools:taskName="TaskOne" drools:scriptFormat="http://www.java.com/java" name="TaskOne">
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