Googling Castles & Crusades for a pirate copy (I gave away my print C&Cs a while ago) I can see the OGL on page 128 of Monsters & Treasure (1st edition, (c) 2005). Unsurprising since the monsters & magic items are mostly taken from the 3e D&D SRD. The preliminary starts with:
Castles & Crusades
128
Monsters & Treasure
129
This book is published under the Open Game License (OGL) version
1.0a by permission of Wizards of the Coast, Inc. The Open Game
Content appearing in this book is derived from the 3.0 System Reference
Document, copyright 2000 Wizards of the Coast, Inc. All contents,
excluding the OGL, is property of and copyright 2004 Troll Lord Games.
All Rights Reserved.
Designation of Open Game Content: The following is designated
Open Game Content pursuant to the OGL v1.0a: all text appearing in the
following sections and subsections, listed by page number and heading
or sub-heading: pages 4-85, "Monsters"; pages 86-127, "Treasure".
Also, the following open game content related words, phrases, and
abbreviations wherever they appear: Strength (Str), Dexterity (Dex),
Constitution (Con), Intelligence (Int), Wisdom (Wis), Charisma (Cha),
Class, Fighter, Ranger, Rogue, Assassin, Barbarian, Monk, Wizard,
Illusionist, Cleric, Druid, Knight, Bard, Paladin, Race, Demi-human,
Dwarf, Elf, Gnome, Half-Elf, Halfling, Half-Orc, Hit Dice (HD), Hit
Points (HP), Alignment, Lawful Good (LG), Lawful Neutral (LN),
Lawful Evil (LE), Neutral (N), Neutral Good (NG), Neutral Evil (NE),
Chaotic Good (CG), Chaotic Neutral (CN), Chaotic Evil (CE), Level,
"to hit", Damage, Experience Point, Saving Throw, Player Character
(PC), Non-player Character (NPC), Turn Undead, Spell, Arcane, Divine,
Magic, Spell Resistance, Item, Equipment, Armor, Weapon, Potion, Rod,
Staff, Wand, Scroll, Ring, Wondrous Item, Artifact, Cursed, Bonus, d4,
d6, d8, d10, d12, d20, d%, round, and turn.
Designation of Product Identity: Product identity is not Open Game
Content. The following is designated as product identity pursuant to
OGL v1.0a(1)(e) and (7): (A) product and product line names, including
Castles & Crusades, Castles & Crusades: Player's Handbook, Castles
& Crusades: Monsters and Treasures, Castles & Crusades: Castle
Keeper's Guide; (B) logos, identifying marks, and trade dress; (C)
all artwork, logos, symbols, graphic designs, depictions, likenesses,
formats, poses, concepts, themes and graphic, photographic and other
visual representations; (D) logos and trademarks, including Castles &
Crusades, Castle Keeper, SIEGE engine, and Troll Lord Games, or any
other trademark or registered trademark clearly identified as product
identity by the owner of the product identity, and which specifically
excludes the open game content.