What are the actual OSes that are considered a "Windows Server" by IsServer of NSIS LogicLib WinVer?
Wikipedia lists the following as belonging to the Microsoft Server family:
But not:
Does IsServer share the same opinion?
The IsServer documentation also includes NT as a "server", contrary to the Wikipedia article.
IsServer is true if OSVERSIONINFOEX.wProductType from GetVersionEx is not VER_NT_WORKSTATION.
NT4 and 2000 had both client and server versions of the OS.
This page claims you can detect home server by checking for the VER_SUITE_WH_SERVER bit but since the test for 2003 (GetSystemMetrics(SM_SERVERR2) == 0) is clearly wrong I don't know how much you could trust this information. (Checking for 2003 correctly means checking that the version is 5.2, not VER_NT_WORKSTATION (XP64) and only if you need to tell 2003R2 apart from 2003 would SM_SERVERR2 come into the picture)