The Celts did arise in what is now Czech territory, but it was a very long time ago! The Celts since moved westwards and eastwards, and established communities as far apart as Galicia (spain) and Galatia (Turkey). Unfortunately, they were essentially pushed out by Germanic, Dacian and Roman groups, and ended up where they live today: Ireland, Britain, and places colonized or settled by Irish or British people (This includes Brittany, which started out as 5th-6th century settlements of British refugees).

It is true that historians and archaeologists are divided as to whether these early groups were identifiably "Celtic," because "Celtic" today is a linguistic designation, and these people left almost no writing. From what we can determine from place names, and from the comments of Classical travelers, these people were related to the ones who later spoke Celtic languages. That's the best we can say definitively.

In any case, there was no Celtic culture left in the Czech republic for the communist regimes to suppress, unless you want to count the odd place-name! It became trendy in the 1970s to call yourself "Celtic," especially in folk music circles, so every country tried to jump on the bandwagon. Like Galicia, which has very little cultural similarity (and almost no linguistic links) to other Celtic countries, the Czechs want a piece of the Celtic music action!

I'm not saying this won't be a good festival. For one thing, they could get the top groups from Celtic countries. For another, they might hold it at an interesting archaeological site, or provide directions to one. That's where you'll see real "Czeltic" culture!