VS2012 Script Task - can't find assembly though it's in GAC

Hi

I've found lots of past questions on this, but they seem to relate to earlier versions.

I'm using VS2013 SSDTBI to develop SSIS packages; target server is SQL2014.  The Script editor that opens from the Script task is VS2012, for some reason.

I'm trying to add a reference to Microsoft.AnalysisServices, which is happily sitting in the GAC.  Output of gacutil -l gives this:

processorArchitecture=MSIL
  Microsoft.AnalysisServices, Version=10.0.0.0, Culture=neutral, PublicKeyToken=89845dcd8080cc91, processorArchitecture=MSIL
  Microsoft.AnalysisServices, Version=12.0.0.0, Culture=neutral, PublicKeyToken=89845dcd8080cc91, processorArchitecture=MSIL
  Microsoft.AnalysisServices, Version=9.0.242.0, Culture=neutral, PublicKeyToken=89845dcd8080cc91, processorArchitecture=MSIL

but this doesn't appear in the Project/Add References list.  (The GAC is enormous on this machine - it's pretty certain thathardly anything from the GAC is appearing in the Project/Add References list).

A lot of the answered threads in this forum talk about having to copy the DLL to a specific location: but those answers seems to be about earlier versions.  The documentation here:

MSDN

suggests that I have to add the reference by Browseing the file system.  Problem is there are 20 copies of Microsoft.AnalysisServices.dll on the machine!  Sure, I can cut down this number to get just the V.12 ones, but that still leaves me with many to choose from.  Which one should I use?  Perhaps this one:

C:\Windows\assembly\GAC_MSIL\Microsoft.AnalysisServices\12.0.0.0__89845dcd8080cc91\Microsoft.AnalysisServices.DLL

?

I'm wondering:
- How will the server where I deploy this SSIS package cope with the reference?  Perhaps its GAC is in a different place?
- Why can't I simply add the reference from the GAC?

Thanks for any ideas!