Update 10/10/2018: Kotaku has clarified that "Living the life of luxury" is not a Legend of Zelda variant game, but is rather a "hacked save file" for the regular Legend of Zelda game that was in the NES library at launch.
The full list of inventory items the save gives you includes White Sword, Magical Shield, Blue Ring and Power Bracelet, Blue Candle, a Red Potion, a piece of meat, and three extra heart containers, in addition to a full bag of rupees, bombs, and keys.
So it is kind of like giving Zelda a "New Game+" option, but without having to have completed the game first.
The original story follows below:
When Nintendo announced the Switch Online service, one thing that it promised was that it would regularly rotate classic NES games into the library which subscribers can play for free. Nintendo announced that Solomon’s Key, NES Open Tournament Golf, and Super Dodge Ball would be added to the catalog on October 10.
Today those three games became available, but Nintendo had an additional surprise. A fourth game, The Legend of Zelda was added, albeit with a twist.
The game is subheaded “Living the life of luxury!” It is essentially Zelda on steroids. Players will start the adventure with a “ton” of rupees and several powerful items such as the White Sword, the Magical Shield, the Blue Ring, and the Power Bracelet. Players may also choose to purchase more items.
It seems a bit like it defeats the purpose of the game, and in a way it does. However, upon finishing the game (which should not take long with the given head start) players unlock “Second Quest.” Second Quest is a “more difficult version of the game.” Apparently, Nintendo wants to make the game a bit more relaxed for any Zelda noobs who might be playing.
Today’s additions bring the NES library up to 24 games. The original 20 include classics like Donkey Kong, Double Dragon, Dr. Mario, Super Mario Bros, and Tecmo Bowl. You must have a Switch Online subscription to access the games. Plans include $4/month, $8/3-months, and $20/year.