What does it mean? What's the difference?
10 man strict means we run 10 mans with 10 man gear, we do not allow any gear from current 25 man content. To enforce this and allow us to be tracked as a 10 man strict, none of our guild members are allowed to run current 25 man content. There are no exceptions to this.
If you want to run ICC25 (even in PUGs), do not apply to this guild. If you have run ICC25 in PUGs before, also don't apply as we will be unable to accept you. If you are truly interested, wait or reapply after the next content patch when current 25 content is allowed to be run.
ICC10 drops iLvl 251 Gear and Frost Emblems. This means you can run things that drop gear equivalent or lower than 251. Onyxia 10 and ToC 10 both drop 232, so that's obviously fine. Onyxia 25 and ToC 25 drop 245, so that's fine too. (However you will have to PUG those). ToGC (ToC Heroic) 10 drops 245, so that is perfectly fine as well. ToGC 25, however, drops 258, so that is off limits. Since ICC 10 drops Frost Emblems, the 264 Frost Emblem gear is fair game, as is the BoE 264 gear.
From Guild Ox:
"What are the 10-man 'strict' rankings?
The 10-man strict rankings show the achievements of pure 10-man raiding guilds. A 'pure' 10-man raiding guild is one that does not participate in 25m progression content. We recognize that 25-man guilds or guilds that regularly participate in 25m pug runs often have a distinct advantage since they can gear up at accelerated rates and move faster through 10-man content. Consequently, our 10-man strict rankings exclude guilds which access any 25-man content that offers higher ilvl gear than what the current 10-man normal content provides. If you are a 10m guild that has members which want to run 25 man pugs then the 'strict' classification is not for you.
What is the 10-man 'strict' criteria?
Guilds will be excluded when they earn any Icecrown Citadel (ICC) 25 normal kills or any TotGC 25 hard-mode kills. Guilds must also have their 10M Progress World Rank be better than (lower than) their 25M Progress World Rank.
But ICC 25 normal drops the same iLvl gear as ICC 10 hard mode, why can't we run ICC 25 normal and stay 10m strict?
It is true that ICC 25 normal drops 264 iLvl gear and this is the same iLvl at ICC 10 hard mode. However, guilds can gear up at twice the rate if they run ICC 25 normal and this is clearly an unfair advantage - GuildOx ranks guilds based on the rate at which they earn achievements/kills. Yes, we understand that you can get iLvl 264 gear from Emblem vendors and other sources, but we have drawn the line at ICC 25 normal."