Abstract
It is not difficult to find that when downloading a software and ready to use, a pop-up window appears. The contents of the pop-up window are some terms of use agreement. Clicking on "agree" means reaching an agreement with developer of the software. In a traditional sense, the agreement is like a contract between the developer and the user. Professionally, it is the software developer that agrees the users to use its software, which is called "authorized". In terms of licensing, the situation of different software is not the same. The most common is that some software are free to download, while some need to pay for download.
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