I've just uploaded version 1.0.2 of the Membership plugin - this version, along with a few enhancements, hooks and filters (yes more) has an extra file in the archive for users of the premium version of the plugin to transition over to (and finally stop the nags between the lite and premium versions).
Steps to complete:
1. Grab the latest zip file from here - https://premium.wpmudev.org/project/membership
2. Unzip and upload to your server - if you are installing in the standard wp-content/plugins directory, navigate to the plugins page, select to view all plugins, and you will now see two listing for the Membership plugin.
Membership Premium Old version which will be activated and
Membership Premium which will be inactive.
3. Activate the Membership Premium plugin - you should now have both activated and visible in the list.
4. Deactivate the Membership Premium Old version the Old version should now disappear from the plugin list and you will be running the only version left in the plugins list.
5. You can now FTP into your server and delete the membership.php file from your membership directory (leave the membershippremium.php file in place) - this is optional as there will be no issue with it remaining in place.
This upgrade will be the last time this will have to be done, but is necessary to split the premium and lite versions.