What they are referring to is a rule-set that is either extremely rigid, in the case of static, or a little more malleable, as is the case with dynamic.
I will use the article's example to explain a little bit further:
A static policy
could require that no individual who can serve as payment initiator could also serve as
payment authorizer. This could be implemented by ensuring that no one who can perform
the initiator role could also perform the authorizer role.
So in this case, the static policy concerning separation of duty would not allow one person to assume to role of payment initiator AND payment authorizer, even at different times. They could either initiate payments, or authorize them. This rule is rigid, meaning that they couldn't assume one role or the other, they are ONLY an authorizer or ONLY an initiator.
Example: Bob is the initiator, and Becky is the authorizer. If Becky doesn't show up to work, Bob cannot assume the role of Becky, the authorizer.
Now a dynamic policy:
More flexibility could be allowed by a dynamic policy that
allows the same individual to take on both initiator and authorizer roles, with the
exception that no one could authorize payments that he or she had initiated.
So in this case, the dynamic policy concerning separation of duty would not allow one person to initiate payments AND authorize them. They could either initiate payments, or authorize them. Since this is a dynamic policy, they could assume either role as necessary, but they could not assume both roles simultaneously.
Example: Bob is the initiator, Becky is the authorizer. Bob doesn't show up to work. Becky can step in for Bob to initiate, but CANNOT authorize the same payment. Someone else would have to authorize the payment, a third party, Bill. (Or wait until Bob comes back)
The long and short of it is: Static policies separating duties are rigid, your role is your role and you cannot "wear someone else's hat" in order to complete a task. Dynamic policies separating duties are less rigid, and allow for flexibility, but would never give complete control of a process to one individual.