Is it possible to buy software sources on codecanyon.net, add a little and use it for commercial purposes?

Question

Law in IT

Good evening, dear experts
Situation
There is an idea of ​​one useful software that we are going to massively promote and use for commercial purposes, and lo and behold, we found the source code for such software on codecanyon.net, the program found there suits almost everyone, there will not be much additions.
Questions :

• Is it possible to buy the source codes of any program presented on codecanyon.net with such a license initially that it would be possible to supplement the software a little and receive commercial benefits? (explained "crookedly", but experts will understand)
  
• Is it even possible to take any software with open source, supplement it with a little of your own code, consider this program as your own and issue all the necessary rights to it, and accordingly get the right to benefit from it?
  
• Where can I read information about the use of someone else's code for commercial purposes?
  

Thanks

Answer 1

Is it possible to buy the source codes of any program presented on codecanyon.net with such a license initially that it would be possible to supplement the software a little and receive commercial benefits? (explained "crookedly", but experts will understand)

At first glance, your needs require their Extended license . It can be modified, used for commercial purposes, but there is a License-per-product. We need to look in more detail.
No, far from any software, even if it is open source, you can modify it, use it for profit, etc. These questions are prescribed in the license under which the software is distributed.
To make our life easier (and safer) there is a whole set of free software licenses (GNU GPL, Apache, MIT, etc.). Although it is always possible to distribute under your own license with "fine print and kickbacks".
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