How does one appeal to proprietary software enthusiasts? The recipe is very simple. Build a software of any variety, anything entertainment focused is an ideal place to begin. From the final feature set, remove some or many of the basic characteristics that this software would naturally possess. Inform the user that in order to access these "extras", they must first jump through some hurdle. This can be anything from conventional subscriptions to in-program status signals for their peers to fawn over. Divide it up into many smaller parts, closed software supporters *love* playing collect-'em-all.
And for good measure, make sure that it must check in with your master server periodically. Many proprietary software advocates do not consider a program to be legitimate unless a sort of connected account must be created and signed in before being allowed to use the program or its extra features. Tell them that this is a social feature which enhances the experience.
Lastly, always make sure that all of the time and effort which your users will be sinking into this program will be saved into incompatible proprietary formats, ideally server-side, so that they can never leave lest they eat the sunk cost. Keep them ignorant to all of these practices and if they ask questions, always reassure the users that it has been setup this way in order to protect them or to add value to the product.
Install a rootkit on their computer. Tell them that it was a security measure.
Display adverisements directly within the interface.
Make them use their real name and image.
Get them to pay for doing things that they could previously do without any restrictions.