Old chess software

Accessing old chess programs, and indeed any old games, without payment is a bit of a grey area. 'Abandonware' is the term used for software no longer being sold or supported, and there are a number of sites on the net that allow you to download or run these programs. I suspect that the copyright on these programs is still in effect, but on the other hand, how can you pay for such programs if there is no one to pay.
Having got that out of the way, I did come across a site that had a number of old, and historic pieces of chess software. https://www.myabandonware.com/browse/theme/chess-d/ has around 75 chess (or chess type) programs listed, and can either be downloaded, or played inside a browser. Various versions of Battlechess are there, as are early copies of Chessmaster. Of course these games are the MS-DOS versions of everything, so the graphics (and strength) aren't that great. The earliest program listed was MicroChess (1978) which ran on the Apple II (so you'll need an Apple II emulator to play it). The earliest DOS program listed was simply called Chess (1981), but you can play that in a web browser (NB on the easiest level I checkmated on move 5)
If you do a bit of extra searching you can probably find more programs that weren't tagged correctly, as well as non-chess games you probably never thought you'd play again!