There is no seed for the Silver Dungeon, as Dungeons do not require seeds, and the Silver Dungeon hasn't been released yet
Noone knows but the Lore. (who is problebly based on Liberty)
also will the original mod be rereleased?
By original, you mean the Aether 1? No.
The Aether 2 is supposed to be an update to the Aether 1 series, so they won't bring it back... But all of the cool features of the Aether 1, such as the Gold and Silver dungeons should be brought back to the mod very soon.
Adding on to that a little bit for anyone who doesn't know, Gold and Silver dungeon will be added back sometime later but it will most probably have a different name and deisign for the dungeon.
A form of the silver dungeon will be returning in the Aether 1.6.4 mutation beta release. https://www.facebook.com/photo.php?fbid=601020039978119&set=a.216761868403940.52790.172320626181398&type=1&theater
No Silver or Gold Dungeons in Aether 2. They should probably make something similar for those in the Aether 2.
I have seen the Silver Dungeon in Tobuscus's series, butn ever found it myself in Aether I or Aether II