App.cpp, line ~10:

#ifdef PLATFORM_WIN32
String GetEnv(const char *id)
{
	return FromOEMCharset(getenv(id));
}

[...]

App.cpp line ~20:

#ifdef PLATFORM_POSIX

String GetEnv(const char *id)
{
	return FromSystemCharset(getenv(id));
}

[...]

Util.cpp line ~620:
String FromOEMCharset(const String& src)
{
	WStringBuffer b(src.GetLength());
	int q = MultiByteToWideChar(CP_OEMCP, MB_PRECOMPOSED, ~src, src.GetLength(), (WCHAR*)~b, src.GetLength());
	if(q <= 0)
		return src;
	b.SetCount(q);
	return WString(b).ToString();
}

String FromWin32Charset(const String& src, int cp)
{
	WStringBuffer b(src.GetLength());
	int q = MultiByteToWideChar(cp, MB_PRECOMPOSED, ~src, src.GetLength(), (WCHAR*)~b, src.GetLength());
	if(q <= 0)
		return src;
	b.SetCount(q);
	return WString(b).ToString();
}

String FromOEMCharset(const String& src)
{
	return FromWin32Charset(src, CP_OEMCP);
}

String FromSystemCharset(const String& src)
{
	return FromWin32Charset(src, CP_ACP);
}