Hi Rick,
basically the expiry date means that the particular version of SharpCap 3.2 beta you are using will stop working on that date. By then there will either be a newer beta verison (with a longer expiry date) or the stable non-beta 3.2 available, so all the expiry date is doing is making sure that you upgrade to a newer version of SharpCap 3.2 by the end of September.
The reason for the expiry dates in the beta versions is to avoid the situation that I used to have where someone would report a bug and I'd find that they were using a beta version from nearly a year ago and I'd already fixed the bug 9 months ago...
cheers,
Robin