The premium package is lifetime license that mean if you download and install the license didn't require any monthly or annually fee.
As per license and agreement OPENTEKNIK LLC, COMMERCIAL LICENSE v1.0
clause 5.
Upgrades, Updates and Fixes: Premium license holders will have 6 months of technical support, access to the API, and any new updates released for the premium software. Any premium features included at the time of purchase of the license or through the 6 month update process are included indefinitely. After the 6 month period expires, a updates could be purchased.
Our developers work with love and efforts to make the product better and make the bug free updates available to the customers. These updates are provided for 6 months free of charge when you purchase premium social network. This includes some other services like mobile api , sentimental api.
If your 6 months period expired our system asks you to renew the support to download the updates. You can renew and get the updated version. You do not need to purchase premium social network again.
If you wish to upgrade only core you can get download the core framework free of charge but note that this core update didn't contain premium updates.
In case you lost premium social network files this also applies in that case..
Download :
v7.6 Core Update : https://www.openteknik.com/cores/core-v76.zip