Are you asking about upgrading to mSecure 5 from a previous version of the app? If you are, mSecure 5 is a new app, and it is a paid upgrade. Also, for clarification, there has never been a recurring membership charge for any of the mSecure apps. They are just one-time purchases.
When we created mSecure 5, we created a new app, with a one-time purchase. In order to use the app, even if you are an existing user of mSecure, there is an upgrade charge. We left the mSecure 4 app going for some time after the mSecure 5 app was released, because we didn't want to force our users into using mSecure 5, mostly because it was a paid upgrade. About 3 years ago, we stopped supporting the older version of the app and focused all of our development energies into mSecure 5. Up until now, there have been no problems with mSecure 4, but recent iOS upgrades have started causing problems with the older version, so we've been letting our users know they should upgrade to mSecure 5. It's not mandatory, but it is highly encouraged, because we don't know when mSecure 4 is going to break for good in future versions of iOS.
I'm not sure if that answers the questions you have about mSecure 4 and 5, but if there is further clarification needed, please let me know. Also, since you are an existing user, we do offer a 50% discount off the full price of $29.99, so if you are interested in purchasing a license, please let me know and don't purchase it from the App Store. The discount is only available when purchasing from our website.