Okay, just tested with all the released versions (Excluding Betas) back to VPN 1.2.3. (Released with WinGate 5.2.3).
In all cases, the version 6 builds did not give that warning. The version 5 builds did. So, you have one of two options - use the latest version (Recommended) - especially because you can use your existing license key (And if you're trialing - best to use the latest version)
Alternatively, use this post - it describes the registry changes required.
http://forums.qbik.com/viewtopic.php?t= ... hlight=ics