[diagso]

will it work on the same computer with esysx?

Yup, works fine. Remember that BU is not a launcher, it's add on for Esys. I run on one laptop EsysX @ 3.34, EsysPlus @ 3.36 and 3.39 esys with BU no problems. Just don't mix C:data and you'll be fine.

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will it work on a clean system or computer where there is no esysa isty, etc.

You need Esys installation to code the car somehow, but BU is providing link to Esys for installation. 

To run Esys you don't need ISTA, StandardTools and so on. Just Esys, Enet and BU to modify files read from the car.

PS. If you plan to use diffrent laptop to read/write files to car via esys, then you can just install BU. In such scenario you're going to miss out on some nice functionality of the tool.