Depends on how you define "communists" and "terrorists". If you say communists are members of the organisation called Communist Party (including main - USSR - party and foreign branches) and terrorists are members of an organisation like Al Qaeda that has terror as its tactics - then yes, they are - or, more correctly, were - nearly equivalent. Communist Party's official goal - at least back in the middle of the last century where it was at the peak of its power - was the overthrow of the capitalist governments, or at least sufficient weakening of them to render them unable to interfere with the Party's goals. In the service of this goal, they did not hesitate to use violence, murder and any other criminal activity. They also waged a multitude of actual wars in many places, including against the US and US allies. Of course, not every rank Communist Party member was engaged in active violence - but also not every rank member of terrorist organisation blows himself up in Baghdad market or flies a plane into a New York building. There are many supporters and enablers that contribute their part to make the final strike possible - by giving money, material support, logistics, cover, etc.
Of course, now that communist parties are mostly a sad joke, the equivalence is absent, but back in the day I would say being a communist - especially outside of Communist block were you didn't have much choice and also almost always did not possess relevant information to make correct conclusions - was not much different on the substance than being, say, Hamas supporter now, even though I realize many people did not understand that. But many people don't understand it now too.