Guild Wars 2

Do you get the guild commendations if you are guesting on a server?
Do you get the guild commendations if you are not in the guild that activated?
Do you get the guild commendations if you are guesting and are not part of the guild that activated?
Do you get the guild commendations if you are in the guild that activated but your home server is not their home server?

No. No. No.

Guests to a server will get only the dynamic event reward. They are not able to see the mission status, nor are they notified that it has started. If they participate they will only receive dynamic event reward (some silver, karma exp) no commendations.

People assisting a guild (even not guesting) again only receive the dynamic event reward.

And combining 1/2 you will not get commendations from guesting and not being part of the guild.

And no, for the final question too.

You must
1. be in that guild
2. be representing
3. be from that guilds main server (no guesting)
in order to get commendations. Anyone else only get dynamic event rewards.