say a company is using Open source libraries, or programs, and packaging it into a proprietary solution. or perhaps, the engineers have copy pasted certain section of those open source libraries and have compiled it now, into a very useful "proprietary" software suite.

what legal troubles will this company face if any ? are you allowed to do this ? i mean the customer doesn't see the source codes, only runs the binary files on their computer.

for example, i find an excellent NLP library in python, and decide to use it in my program that i am selling for $4000 USD (i write like 10 lines of code and let the library do the work). could i get into trouble ? would i need to write the NLP library myself from scratch to be considered "proprietary" ?

danke