legal drivers on ubuntu 18.04 LTS

im just new to linux and only used to windows, so after i installed ubuntu and found out that i can’t use my gtx 750 ti driver CD as im used to, i opened “software & updates” -->> additional drivers and chose the latest driver

my question
is this way to install my graphics card driver legel ? is i’ve read it’s not. if it’s not what is the “legal” way ?

Using ‘software & updates’ on Ubuntu is the correct way to install the driver. This way you should always have a working driver version. If you want to have the always latest driver, you can add the Ubuntu graphics ppa : and install the driver from there. But currently, version 418 is the latest. You should never use the .run installer from the Nvidia website.

so -not being trying to be importunate here but -it’s the appropriate way ok. but it completely legal ? also why downloading the driver from Nvidia website is wrong, should not it be the perfect way ?
Thanks in advance :)

Yes, it’s legal. The nvidia driver is redistributable and Ubuntu is allowed to repackage it.
Dowloading an installer from web and install it is Windows-style-correct, but for linux doing this needs you to know exactly what you’re doing.