Translation:It is full
Li = Ji/Ma subject prefix
Me = in this case it's a state of being, so takes -me- instead of -na-
Jaa = fill/to be full
Note that I don't think the verb kujaa refers to full as in satiated, but more abundant. So you might have jagi limejaa, "the jug was full", but not nimejaa for "I am full" (I think that would be nimeshiba).
Because " me " it is perfect tense and also...I don't know how to call it in english...static form (?) , describing a stane of the thing but in this case rather it should to be translated - it is filled. I don't want to touch your kenyan friends but if I see some tanzanian woman TEACHING kiswahili in TV and - she is doing the basic mistakes....So sorry but I prefer to base on books or similar materials :) From another side - you are right telling how the aborigines treat the linguage because it is mainly for communicate with them, isn't it ? :)
I think my sources are quite reliable, since he has a degree in Swahili literature. But yes, I have also seen quite a number of less than perfect teaching also. The thing is, the sort of mistakes they make is usually not a mistake in the Swahili language, but rather in translating it to English. If you think about it, the perfect tense in English does also function as a present form describing a state of being finished with an action rather than acting right now. Both in Swahili and in English there also exists a past perfect tense, describing the situation where an action had already been finished in the past. An example in English "As I entered the house, she had already left.", and in Swahili "Nilipoingia nyumbani, alikuwa ameondoka."
No, in Swahili it is actually considered to be present time, and it describes a state rather than an action. You could say it is the state resulting from an action. The action is of course in the past, but the state is present. Another example is "nimechoka" - "I am tired".
You could say that the glass "has been filled", but kenyans, at least the ones I've talked to, understand it as something that is now rather than something that has happened in the past, as we often understand the perfect tense in English. It took me some time to understand this, but it is actually quite logical when you think about it. When I asked my Kenyan friends about it they would always say that the "-me-" form describes something that has happened "just now" but isn't still going on.
'it is filled' is in present simple passive voice, which means it's continuously occurring, which is not the meaning of 'limejaa' (the action has already been completed, sentence is in active voice). The passive form of this, which would be 'it has been filled' is 'limejazwa'. 'It is filled' would translate to 'hujazwa' (habitual)
It's present perfect. The action itself, the filling, was done in the past (near or far). But the state of being filled, or in other words being full, is present. The kenyans I know are very clear on the matter that it is describing something in present tense, and not past. It's quite interesting, because it shows how we think different about these things.