Hear's what it amounts to:
Artifacts (including collection and spawn replicas) and event items can have however many the devs feel like (I saw a dev go on test center Yew Fel gate with a butcher knife with 100% intensity EVERYTHING, naked with his god mode on, when at the July 2007 Town Hall in Columbus, Ohio - it was funny watching a ghost chasing him, repeatedly saying "WTF ARE YOU???" to a dev). Most, however, are limited to 5 or 6, and cannot gain any more via other means.
For crafted weapons, Exceptional quality will have up to 40% DI on most shards, 43% on Siege Perilous & Mugen. (35% Base, plus Arms Lore bonus)
The chosen meterial for crafting/enhancing an item can add 1-3 more (3 being more on armor, than weapons, as they get resists PLUS the kind of stuff that they add on weapons, for metal), with "elemental damage" counting as ONE property, no matter how it is split up between physical/fire/cold/poison/energy. Note that most artifacts & event items cannot be enhanced. The ones that could typically predate the property system as it was introduced in Age of Shadows, and were duped heavily so people could experiment with enhancing them. (note that the items from the Dread Knights of Spring 2008 are rare exceptions, as the shields could be enhanced, and maybe the swords)
Both the above properties can occur as random properties on magic(looted) or runic (crafted) weapons, though the DI property is rerolled on runics if it comes up less than the intensity that being exceptional gives (provided the item is exceptional). The Runic & material properties usually stack (though the elemental damage stacks in a precise order, but in an odd-looking sort of way).
Note that Spell Channeling & Faster Casting stack in such a way that SC with FC negative 1 is ONE property, while SC with no FC showing is TWO properties (and if you get SC WITH a +1 bonus, you are either looking at an artifact, event item, or a recipe item that gives FC 1 combined with getting SC with no penalty as two runic properties)
Non-artifact Recipe items will have their own properties - usually 1-2. The Artifact recipes don't combine with runic, material or exceptional bonuses, for the most part (the wooden armor combining set being an exception, that allows material bonuses).
Best case scenario
5 Runic properties unrelated to the item being created.
Exceptional Weapon DI
2 properties from being made of a specific metal (Durability, lower requirements, elemental damage and/or 40 luck) or wood (only archery recipes & wild staff variants have recipes), but most of of these are useless unless stacking with runic properties.
2 properties from recipe (again, you'd usually rather have these stacking, rather than standing alone at their low base amounts from the recipes).
So, theoretically, 10 properties, and could show FIFTEEN lines of properties overall, if gold/dull copper (2 materials with 2 properties but no elemental damage), elemental damage having at least 10% in each, as one property (5 lines for 1 property) and Spell Channeling -1 (2 lines for 1 property). But it would probably be a sucky weapon, with lots of small values in a lot of properties too low to be much use.
