Is it possible to modify someone else's game/program?

Question

Programming

Dear experts, attention to the question.
Is it possible (in theory) to add your own modifications to the game / program?
Well, let's add a virtual camera (invisible to players) to CS:GO that displays the image on a separate screen (on my second device). Something like that.
Or add your own modifications to Photoshop.

Answer 1

If the program provides an interface for plugins / modifications, then you can. The same photoshop - provides. CS:Go in some form - too.
If it doesn’t, then:
1) It’s difficult - you need to be able to program and understand the subject area
2) Most likely it violates the license agreement

Answer 2

Always possible, but difficult.
In terms of license - you can, if you do this with your purchased copy, and you have all the rights to use it, excluding distribution of the purchased copy for any purpose.
Example: If you bought an iron - you can use it as you like, also with the software.
The difference is only in an attempt to copy using tools to remove copy protection and / or further use of a copy of the Software in order to obtain financial benefits. Those. this is a steal.
Otherwise, you can do whatever you want with your legal copy of the purchased software for personal purposes.

Answer 3

Of course you can.
Especially looking at similar articles where they make bug fixes without source code in Batman

Answer 4

Can. But be careful.
In the photo#op example - if your modification allows you to run it without a key or other binding to a license - it will be regarded as something falling under Criminal Code
273. You can sit down for this :) game, then at best they will be banned, and at worst - the same Criminal Code 273