I am brand new to StackApps, so please bear with me for a question that is hopefully obvious to most regular users.
As far as I can tell, there is no charge for accessing the StackExchange API. Apparently, even registration that brings increased usage permissions does not incur any charge.
I would like to know this for sure, but surprisingly, despite searching for quite a while, I cannot find any documentation anywhere that definitely says that the StackExchange API is free of charge. In particular, I would expect something mentioned in the API documentation or in the terms of use, or even in a prior question to StackApps, but I can find nothing anywhere.
So, could someone please tell me definitely: is there any fee to use StackExchange API or is it completely free of charge?