Since you posted on forum same message you sent via our contact form, I am attaching part of our response for readers:

The version you downloaded was the latest workable version at the time of purchase.

This version although tagged as RC is stable and has been around for over a year
and used by many users.
It is not "unworkable" as you stated.

Regarding your surprise to not have access to newer releases, please note that the
one-time purchase item description (which you see when you purchase such items) reads
as:

---

Purchase current version individually

Pay to get the current version of add-on(s):

This is a one-time purchase
No maintenance releases
No priority support as in our Advanced or Professional memberships
Once the payment is completed, an email message with purchased package will be
sent to your email address

Note: All of the following add-ons are included in the Advanced or Professional membership
together with maintenance releases and priority support for 12 months.

---

In order to improve this wording perhaps you can suggest modifications, so other
users are not also surprised?

Please note that we have Advanced and Professional membership subscriptions that
do provide 1 year maintenance access to new releases and priority forum support.

Thanks again,
Nick