In plain English, some of the [leaked] terms outline how users are waiving some of their rights to the game and giving them to YoYo Games when the game is submitted and uploaded to their site. Essentially YYG would have rights to use a submitted game in most cases, however it wants. They are even able to request that it is modified to their liking, and if you can believe it, possibly even sell your game! It appears as though this wouldn’t require any permission on your part, although it is unlikley YYG would do this without your permission.
In summary, unless you want to give many of your rights to your creations up to YoYo Games and let them benefit from using the game everywhere, changing it, and possibly even making money from it… you may want to choose an alternative site to host your games.
Note 1: The source of this news cannot be confirmed as the user was anonymous. However, a moderator later confirmed that the terms that are being referred to in this article are genuine [ see comment below ].
Note 2: The terms and conditions have many similarities to the terms found here http://www.perplexcity.com/about/terms/. This may either indicate YoYo Games is planning to base their license off of this current one.