Play over 300 emulated DOS games in your browser (PCGamer)
The team over at RGB Classic Games is giving us our nostalgia fixes in the form of Java-based DOS emulation. They currently host over 300 games from days of yore including Doom, Commander Keen, Earthworm Jim, and many more that didn’t get spotlighted because they were too far down the alphabetically-organized page. And it’s totally free.
It almost seems too good to be true. You might expect the hammer of legal action to be looming just above the dusty library of classics, but the site’s intentions appear noble. As it explains: “The highest ideals of this site are to support the authors by providing links to their web sites and ordering information for the full versions of games that are still sold, and to encourage the authors of classic games to preserve their games for future generations by making them available for sale or as freeware. If you enjoy a shareware game, please consider buying it from the author.
“All of the games on this site are freely distributable because they are shareware, freeware, or because the copyright holder has officially and legally released all rights to the public domain (abandonware).”
Assuming that’s the case, the site shouldn’t see any problems, but if it does offend a copyright holder, we’d expect a simple removal of the game in question to suffice. Cue up some Nirvana and have a look for yourself.
Source: http://www.pcgamer.com/2012/12/05/play-over-300-emulated-dos-games-in-your-browser/
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Who knows if it's gonna last, so go play while you can!
= new reply since forum marked as read
a few years earlier wanted to do a Mario Bros. port for PC, after John Carmack had figured out how to fluidly scroll horizontally on a PC. But Nintendo wouldn't give them the license, and so they ended up making the Commander Keen games instead (which are available, but I don't know how similar they are).
When I was a kid I played I played a game on my Commodore 64 that was called "The Great Giana Sisters" (notice the parallel 
. It was made by a German developer, but had to be pulled off the shelves after legal threats from Nintendo. The game spread like wildfire though amongst C64 users, because (a) it was a great game, (b) it had some of the best music ever made on the C64 and obviously (c) because there was no official Mario port for the Commodore 64.
For all you 8-bit music aficionados, here's the Intro, which was a separate program that you had to load containing just the title screen and the music. I remember I used to load it just to listen to the music, even without going on to play the game.
Here's someone playing through the game: