Are the old Sega games free to use or they are still under some license?

I just noticed that there are free software to use old Sega games on Windows such as fusion364 (I think it is a free software because it is said at this link, please correct me if it is not).

Now the question is: what about the games themselves? One can easily find some sipped folders or iso files by searching online for old Sega games such as Sonic etc. But is it legal to just download those games without paying any fee and open them with these software on computer and play, or these games are still commercial and one should pay to buy them to play?

Solution 1:

It is illegal to download free copies of Sega’s games. Under US copyright law, works created after January 1st 1978 are usually protected for at least 70 years.

You can legally purchase ROMs for several of Sega’s games via the SEGA Mega Drive and Genesis Classics Collection, or by dumping backups from your own cartridges.

See also:

• HowToGeek: Is Downloading Retro Video Game ROMs Ever Legal?
• Meta Arqade: What exactly does the law state about emulation and ROMs?
• Arqade: Legal ways of playing old games that aren't for sale any longer