Get from: http://www.forwardthinking.org.nz/paypal.html
Features
Secure license checking against a server before Unity3D App will continue to run.
• Freely distribute your Unity3D App (web, standalone, mobile). It can then only be used with a valid license, so it doesn’t matter how many times the App is copied.
All or part of your App can be locked behind the license.
• Have some free stuff, and some stuff available to license holders.
Perpetual or Subscription licenses (in steps of 1 week)
• Flexibility – sometimes you want to keep the price low per week, and provide your App as a service, other times, you want to let people use it as much as they like, until the next major release.
Uses https and post to communicate with the License Manager Service. Further, passwords are only sent in encrypted form.
• A high level of security gives peace of mind.
New versions of your App can be given new license numbers so that people have to upgrade.
• Once you have saturated the market, but have a new, better version, you can encourage people to upgrade.
Completely automated integration with PayPal – purchase occurs without any intervention from you.
• You get an email whenever a license is bought, and regular amounts of money end up in your PayPal account.
Demo time to allow potential buyers to play with your App before purchasing – you set the length of time.
• Potential clients often want to try before they buy – give them a few minutes to have a go with the full App.
Bulk licensing options – a third party can bulk-buy licenses for your App, and then distribute a special code which allows their clients to get a license.
• This is excellent for schools and training institutes, as well as for building other distribution channels.
Quiet mode allows limited time activity of your App
• You can make a demo App that only runs for a period of time (say, a few minutes) or until you revoke the license at the server (allowing people to use the App until a certain date).
Central license management server, but once logged in once, user can be disconnected from the server.
• Offline use of the App is allowed.
User can administer their own details.
• Freedom to setup new passwords (securely), change some basic details, reset passwords, etc.