Star Wars: The Old Republic fans who have tried to created or find a guild at Guild Headquarters

Star Wars: The Old Republic fans who have tried to created or find a guild at Guild Headquarters page must notice that there are 3 types of servers in the page, i.e PvP, PvE, and RP. BioWare just announced that there will be one more server type, RP-PvP. Hereby, the original RP (role-playing) server will becomes RP-PvE server. Below is the difference of the 4 types of servers.
PvE (Player vs Environment) – Players will have to manually flag themselves if they wish to engage in PvP outside of designated Warzones and Open World PvP areas.
PvP (Player vs Player) – Players are automatically flagged for PvP outside of the designated 'safe' areas (such as Origin Worlds, Capital Worlds, and the Republic/Imperial Fleets; see below for more info).
RP-PvE – Players are encouraged to roleplay and act 'in-character' while playing on an RP-PvE server. Players must manually flag themselves if they wish to engage in PvP outside of designated Warzones and Open World PvP areas.
RP-PvP – Players are encouraged to roleplay and act 'in-character' while playing on an RP-PvP server. Players are automatically flagged for PvP outside of the designated 'safe' areas (such as Origin Worlds, Capital Worlds, and the Republic/Imperial Fleets; see below for more info).
Since RP-PvP server is newly-added and it's not available at the official pre-launch Guild Headquarters page, all guilds that built in RP server are placed into RP-PvE servers by default. Players who want to build a guild at RP-PvP server "will need to create their guild manually on a new server once they reach their Capital World (Dromund Kaas or Coruscant)."

Besides, BioWare revealed the general rulesets in PvP server:
We also wanted to expand on what the PvP server ruleset means in The Old Republic. The obvious overarching rule is that in general, if you see a player of the opposite faction, you may immediately engage them in combat.
The exception to this rule is sanctuaries, which are large areas where PvP may not take place, regardless of whether you are flagged or unflagged for PvP. Examples of this are the Origin Worlds (Tython, Ord Mantell, Hutta, and Korriban), the Capital Worlds for both sides (Dromund Kaas and Coruscant), and the Republic/Imperial Fleets.
Source: swtor forum