The entire English phrase "Those who wait upon" (or "Those who wait for") is translated from one word: vekovye (וְקֹויֵ֤). This word finds its root in Hebrew qavah.
If we look at the Strong's entry for this word, we see this:
- to wait, look for, hope, expect
- (Qal) waiting (participle)
- to wait or look eagerly for
- to lie in wait for
- to wait for, linger for
- to collect, bind together
- (Niphal) to be collected
We can see from this definition, that the idea of "waiting on" as in "serving" or "waitressing" is not at all the definition. However, "hope for" is also a bit of a loose translation here (since "to wait or look eagerly for" does signify "hope" in our modern English). That's why most translations use "wait".
Looking at the three possible definitions ("looking eagerly for", "lie in wait for", or "to wait for, linger for"), it's not clear whether it's an active waiting, as defined in the previous two definitions, or more of a passive waiting, as the third definition shows.
However, if we look at the word in context, I'm more inclined to believe it's more of the active waiting:
Isaiah 40:31 (NASB)
Yet those who wait for the LORD
Will gain new strength;
They will mount up with wings like eagles,
They will run and not get tired,
They will walk and not become weary.
With words in there like "mount up", "run", and "walk", and with the result of the waiting to "gain new strength", this seems more like an active waiting.
(This idea also supports the translation of "hope for" since it's more of a active verb in the English than "wait".)
I don't really see any indicator that this is either an active waiting (in eager expectation) or a passive waiting (lingering). It's hard to say. However, the verse in context makes me think it's more of an active waiting.