Indeed, and Copyright etc. still applies, of course. But in most jurisdictions, what you do with a DVD that you bought, in your own home, is totally up to you,

Indeed, and Copyright etc. still applies, of course. But in most jurisdictions, what you do with a DVD that you bought, in your own home, is totally up to you, so you can install the game even if the company that created it no longer exists. Heck, in most jurisdictions you can even legally disassemble the game and remove any form of online activation or similar, if the servers are no longer available