Update 11/28/2012: The content and comments formerly on this page have been removed in light of Jeb's recent comment that modders should "be nice to one another" when he addressed copying at this year's Minecon. (I'm not a modder but am a member of the mod-using community.)
Almost a year has passed since I originally wrote this page; Flowerchild's departure is now old news. There is no reason to continue to fan old flames. Mojang is aware of the situation and has addressed it, so de-escalation is the order of the day.
Much has changed in the interim, and to my surprise Forge hasn't wilted in the face of the impending plugin API. The Forge community is now stronger than ever.
See Mojang addresses copying and Minecraft modder conduct and A statement on Minecraft mods copying features from each other.