The buzz words at the moment as far as intergration goes with MIS's and VLE's (and anything else really) is SIF.
Well, around here it is anyway!
Basically the way it's supposed to work is, each app/system is SIF compliant. Then, there is a SIF agent which is responsible for translating the SIF framework back to (or from) what the application knows.
E.g.
Our vle is a system called Dokeos (really cool open-source VLE. Made by people from france. But fully translated... code is a little hard to follow at times tho).
So, it would work like this...
Dokeos -> SIF Agent -> SIMS.Net (Or other MIS)
and vice versa
SIMS.Net -< SIF Agent -< Dokeos
Communication is live and as the application itself does the processing then data doesnt get corrupted from editing the database direct (not too much of an issue with things like VLE's... but with SIMS you can really mess up the DB if you edit it directly).
As i'm aware, there are no open-source/free agents out there. And i suspect the SIF agent you would use for SIMS or any other MIS's would come with an extra cost.
But the SIF website is
Welcome to the Schools Interoperability Framework Association and i'm slowly making my way through the framework specification and writting an agent to do some things with it. No idea on timescale tho.