The museum is partly correct.
The men in 1944 were fighting in a legitimate army.
Those who fought post 1945 in either the Stern or Lehi WERE terrorists. Those two groups were terrorist gangs and committed acts of bombing, murder and torture against British, Arab and Jewish people.
For the record, they were communists, with Stern openly declaring himself a Bolshevik in 1944. Such people cannot be considered true Zionists, being anti-Judaism at their core and pro-internationalist.