The MTG Forge zip file contains the curiously named file "name-mutator.txt". MTG Forge can use this file to rename all of the cards. I added this functionality after a cease-and-desist letter was send to Sourceforge.net, my previous hosting website. I figured if my program used different card names it would still be legal, I have no idea if this is really true.
Renaming all of the cards has certain drawbacks which makes it unappealing. First, the user has to read the card text for every card. Magic has been around for a long time and people enjoy using their favorite card. If their favorite card is renamed, the user won't know if MTG Forge has it. Second, if MTG Forge showed the originally named card picture it would still be confusing.
I do have to say that creating new card names for the 441 cards in name-mutator.txt was quite challenging. Let me share with you some of the names that I am most proud of. Zombify became Rise Again and Wrath of God turned into Peaceful Solution. I worked the hardest on the lands because I wanted them to make sense.
Mountain : Rock
Forest : Grass
Swamp : Bog
Plains : White Sand
Island : Underwater
Since Mountains make R mana, Rock is a decent substitute. I tried to make each renamed land match the mana color that is makes. Thinking of a synonym for Plains was very hard, so that explains White Sand.
Basically the name mutator file could be used but it makes the game less interesting.