The Deluxe membership is a paid upgrade to player accounts. It gives the player a series of benefit, most noticeable the removal of ads, increased EXP per match along with bonus weapons, maps and tank models. This feature is not present into the Steam version of the game.
In Shellshock Live (Flash version), it features 10 weapons, 10 maps, 2 tank models, x2 XP rate, removal of the ad below the game, and advanced stats. It could be purchased with tank coins, whom could be acquired with an online transaction or by completing Survey tasks.
Into the second game, Shellshock Live 2 (or SSL2), it had the same concept, being able to be purchased through the Store section, but since acquiring Tank Coins on SSL2 is way easier than on the predecessor game, it could be easily accessed by freemium users, wich just needed the luck to grab the coins in crates through the game.
The Steam version of SSL completely removed the Deluxe system, likely because of it's full-priced status.