The user interface has a little bit more eye candy than Forge and Mage currently has more than 800 cards. Mage is written in Java and for some reason many Magic projects use Java, which is my favorite language. (Java isn't perfect but what language is?)
Mage has a number of good features. The best one is that the AI is challenging and much better than Forge's. Mage uses min-max which should enable the AI to make fairly smart decisions. Mage also lets you play against other people over the Internet with rules enforcement, that way you can test you insidious deck against the AI and then pummel other earthlings via the Internet (that's what the i-net was invented for right?).
Some people love multiplayer Magic but so far no other program other than Magic Online implemented it because it was too complicated. The good news is that Mage supports multiplayer up to 8 players over the internet. This is very impresive because more players means more rules interactions and some cards work a little bit differently in multiplayer. The only limitation is that you can't play against the AI in multiplayer.
Sealed and booster draft are always fun and Mage supports both. You can play up to 8 players in either format. The "over the top" feature is that you can play against other players or AI opponents in these two modes, so you can hone your skills in secret before crushing your friends.
Other goodies include a visual deck editor and a collection viewer that lets you flip through Mage's card collection.
Mage bundle.zip (Windows, 17 MB) version 0.7.1 - This includes both the client and server. You need both parts even if you only play against the AI.
To download the card images click on the "Images" button in the upper-right corner. You will also want the mana symbols, so also click on "Symbols", to download them.
Mage FAQ - Answers some common questions.
Mage Forum - Where you can ask more questions.
Java.com - You must have a recent version of Java (version 6 update 10 or greater).
Thanks to the Mage developers: BetaSteward, Nantuko84, Eugen.Rivniy, maurer.it
As always, thanks for reading this crazy guy's blog,
Mage is written in Java and almost runs on Macintosh. There seems to be a problem with the file path and the developers don't have a Mac in order to test and fix the problem. You can get Mage's source from here which uses the Mercurial version control system.