1. The license you have may cover versions up to 5.39, but no such version has actually been released. In the 5.3x range, the released versions were 5.30, 5.31, 5.32, 5.33 and 5.34. Let me know which one you want, and I will provide you with a corresponding download link.
2. Of course you can upgrade also upgrade to latest version if you like. The version upgrade is 50% of the new license version. 5.40 is not the latest version. We have released one version more, it is labeled 2016.2. Note that you can try out 2016.2 for free and it will not give you this error (but it will run with 30-minute run time limitation until licensed).
We have a site licence for the version 5.39 and I have recently Opc Labs Dlls to upgraded to 5.40. but I am getting this error that "Not allowed to run by the license. You might be using a trial license, and the version of the software you are using is obsolete. Obtain a recent version to resolve this problem."