Do AIs need to purchase skills like Computer, Hacking, EW, etc? The text implies that they only need Active Skills for use in drones, but otherwise there's no clear way to do hacking - since it also explicitly states they don't use their Mental Attributes for it.

Hopefully this is just a quick answer.

I assume that by "active" skills the AI text refers to actual physical activities and not "active skill" as in "not a knowledge skill".
I agree that using a term with a given definition in a different subtext is confusing, but I am quite certain that AIs use the computer-related skills just like everybody else does.
If they'd use something else, the book would have to address what they roll somewhere.

Yes, they still need to buy skills. It's just pointing out that most AI's don't have a use for 80% of all Active skills if they don't use a drone.

Actually the text in Runner's Companion says "This limits the usefulness of many Active skills" [emphasis mine]. I guess the task of figuring out which skills those are shouldn't have been left as an exercise for the reader. =i)

Somehow I think the reader should be given the credit that an AI character really shouldn't have much use for the "Climbing" skill.

That shows me never to answer without consulting the book in question first. Yeah, phrased that way, it sounds a lot less ambigous.

also, the stats for npc AI's in unwired list them with skill entries.