Hi,
We have did the same for our software licensing.
However your budget is too limited. anyway following is my proposal.
1. system serial ( usd 50 )
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I will let you know "the commands" to get system serial numbers, later your developers can use these serial numbers to verify licensing. you may chose any of the following
1. hard disk
2. motherboard
3. network cards
2. Issue unlock key (usd 600)
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Your client will install the application, and will send you there system key ( generated by my script ) you will use your licensing script (provided by me) to issue a license key unique for the client.
client will put this key in his / her application to unlock application functionality.
However you development team will be responsible to allow / disallow certain functionality, on basis of my scripts response
3. licensing server ( usd 1400 )
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I will provide a web gui, where user can buy your products along with license key. after installing your product they will enter license key into their app.
app will request server to verify license key and will unlock its functionality on successful verification.
In addition to protecting your application from piracy you can also sale application on installments / rent and can cancel license if client fails to pay.
Please let me know your thoughts
Regards