Warshaper is a prestige class from Complete Warrior, published a few months after 3.5e. I don't know about the rest of the book, but this prestige class in particular doesn't really seem to take the 3.5e revision into account--it claims that, for example, gold dragons are eligible via polymorph as a spell-like ability, while quasits' alternate form ability is "insufficient to become a warshaper."
But in the 3.5e Monster Manual, gold dragons no longer have polymorph. They instead have alternate form. So, can gold dragons still become warshapers (all the way up to 5th level, where they presumably gain multimorph, as 3e gold dragons would due to being able to polymorph "usable less often than at will"), or are they no longer eligible on account of their new method for self-transmutation?
Would the story change if the dragon used its sorcerous spellcasting to learn polymorph and become a warshaper, but then still try to use its warshaper features with its alternate form ability? Or if the dragon were instead, say, a red dragon with the Alternate Form feat from Dragons of Eberron? Or a Monsters of Faerun song dragon, who has alternate form even in 3e, but whose description says it's "an ability much like polymorph self"?