It appears to be installed.
C:\Program Files\Microsoft SDKs\Windows\v8.0A\bin\NETFX 4.0 Tools>gacutil -l Npgsql
Microsoft (R) .NET Global Assembly Cache Utility. Version 4.0.30319.17626
Copyright (c) Microsoft Corporation. All rights reserved.
The Global Assembly Cache contains the following assemblies:
Npgsql, Version=2.0.12.0, Culture=neutral, PublicKeyToken=5d8b90d52f46fda7, processorArchitecture=MSIL
Number of items = 1
