Guild Master
According to WoWWiki a Guild Master (Leader) is "a player character who is the head of a guild. They have administrative control of the guild's operations (via "Guild Control" button on the Guild list window), including giving ranks, privileges, setting permissions to the guild bank, adding/removing guild members, etc."
Within the confines of the Colonial Space Marines a Guild Master is a figurehead that doesn't actually contribute anything positive towards the success of the guild except delegation of responsibilities.
Guild Masters in CSM History
Alys - Charter GM, master of staring at the AH wall. Don't even bother asking her for mage water.
Ell - Alys passed GM to Ell when she lost interest in the game and quit after having to farm meaningless content for the privilege of experiencing the new content. Ell was true to the figurehead GM role by barely attending raids as he finished off Law School.
Zelf - When Ell finally gave up his subscription to focus on RL he passed GM to Zelf as he was the most active officer at the time. As soon as that happened Zelf went from a try hard to not giving a shit overnight. The curse of the figurehead GM strikes again. Zelf maintained the role of GM for the longest duration while CSM participated in competitive raid progression. Eventually Zelf burned out during Ulduar along with most of the other veteran players.
Lutes - After not signing on for like a month or so, Atena demanded that Zelf get on and pass GM to one of the officers so guild management functions could be performed. Zelf chose Lutes for reasons unknown to the writer. Lutes maintained the role of GM for about a month or two before CSM finally gave up on competitive progression raiding during early Trial of the Crusader. Lutes then took the contents of the Guild Bank and divvied it up among his pals. Later Atena would once again demand that Lutes pass GM to someone who gave a shit.
Kendoch - After Atena's badgering of Lutes, he eventually got back online and passed GM to Kendoch. Kendoch had served as one of the most responsible and accomplished officers during CSM's time as a progression raiding guild. Kendoch maintained the role of GM for the remainder of Wrath and through most of Cata. During his tenure as GM Kendoch worked hard to replenish the Guild Bank that Lutes had given away by selling tons of BoEs from the Cata raids. He accumulated such wealth for the guild that he eventually had to create a bank alt, Sadwalrus, to hold the extra gold that he had accrued. Kendoch eventually got bored with the game in late Cata and had started a new job. When he was letting his sub slip, he then passed GM to Atena. It should be noted that Kendoch was the first and only GM to do more than just be a figurehead.
Atena - Atena assumed the position of a true figurehead that has, to this point, lasted for 3 expansions. Atena has been especially suited to the position as he is one of the only CSM members that can be trusted to log on 365 days of the year barring a couple days for blizzcon and other inconvenient traveling. True to the nature of the roll- he has left all administrative raid duties to the other officers with the exception of periodically picking new names for the Guild Ranks. To the writer it seems plausible that Atena will forever remain the GM of CSM as the guild rides the coattails of it's former glory and dominates the casual raiding scene.