planetItemsTemplate
 templateName "Template:LocalMilitiaStrong"
 subTemplates 0
 groups #
  group
   condition
    type "PlanetOwnerIsMilitia", "NoPlanetOwnerWithChance", "NoPlanetOwner", "PlanetOwnerIsMilitiaWithChance", "Always", "PlanetOwnerIsRace"
    param "#=%?"
   owner "PlanetOwner", "RandomMilitia", "Pirate"
   colonizeChance 0, 1
   items #
    item "Psi:Frigate:Light"

I get Groups, Items, Item.

Group I assume means a chance as defined by "param" of that group within a template is used.

  group
   condition
    type "NoPlanetOwnerWithChance"
    param "0.3"

I am guessing the above example means there is a 30% chance that group will be applied to a planet if this template is assigned to the planet as long as there is no planet owner. But what defines whether or not there is a "chance"? Or is it that there will be 30% of that group applied to a planet, or am I just up in the night?

I suspect Owner is Planetowner = defined under planet in .galaxy files' Pirate/RandomMilita sets it to owner Pirate/RandomMilita.

I have no idea what "colonizeChance" defines.