OGL Ancients covers between 2000BC to about 500BC, maybe a bit later, I think. Anything later wouldn't really be usable in an Ancients campaign. Besides, middle ages/arthurian stuff is already covered in the may standard fantasy games and settings out there. I wouldn't mind hearing what others think, but personally I think OGL Ancients accessory books should stick to Ancients stuff.
Not a problem here. I'll leave the premise open for now until I actually start the outline and submit it for approval. Other opinions are still welcome...
The problem with Celtic stuff, at least from what I heard from the ENworld furoms, is that there isn't much info on "true" ancient Celtic mythology. It all comes from Irish, Scottish, British mythology and was created much later, I think durring the middle ages.
Granted, there is some truth to this, from a certain point of view, but most beliefs, mythos, lore, etc. were passed on as oral tradition and not written down until much later in life. This is no different in Celtic mythology as it is in Judaism, Christianity or Chinese mythos.
Also, true Celtic traditions span all pre-historic British (Irish, Scots, Welsh, etc) origins as well as Germanic, Indian, and the sort... thru the Roman Empire. It's all intertwined. Everything is. It's our culture. It's our heritage.
As for "true" mythology... I realize you mean "specifically Celtic" and not "True & False"... but I'll tell you that from my understanding and studies, even the term Celtic itself is of later origin than the people it represents. Sort of like using the terms "Indians" or "Native Americans"... whichever is more politically correct or exact... in truth, neither are accurate because the land they were indigenous to when discovered was neither than named after India or Amerigo Despuchi... nor were they actually from the land originally... they could be refered to as "Mongols" if in fact there was a land bridge and that is how people got to North America.
Anyhow... Celtic mythology does begin and fit snuggly within the parameters of 2000 - 500 BC. The fact that it doesn't go earlier in time is irrelevant to actual game play unless a group of players is attempting to travel the entire known world. In which case, the GM can make appropriate adjustments where necessary. Also the fact that Celtic mythology penetrates into the Middle Ages can be exempt to the sourcebook as well because it's not needed in the context of OGL Ancients. Therefore, the influences of the Anglos will be minimal and it'll be a truer barbarian, purer Celtic mythos... and less influenced by outsider traditions. The only real influences will lie with Rome... which is already part of Ancients and will further tie the two together.
Besides... didn't you, ShadowDragon, post a desire to see a Celtic supplement?! I thought I was helping you out here!