I don't really know about namecoin, haven't looked much into it yet, so can't help you there.

Regarding creating an alternative currency, yes and no. For someone technically proficient it would be pretty easy to fork the bitcoin source, make necessary changes and start a new whatever-coin with a new blockchain. Looking at it that way, creating an alternative currency is easy. But it depends on how you define currency. For most people, I guess a currency will only be a currency when enough people place value in it, to allow trading with a sufficiently large amount of other people. That's the hard part