This function signature is relative to 0.8.8 API http://nodejs.org/docs/v0.8.8/api/fs.html#fs_fs_writefile_filename_data_encoding_callback. This node definition file has been created to node 0.8.8. 

According with [How to contribute](https://github.com/borisyankov/DefinitelyTyped/wiki/How-to-contribute):

> Definition files should be called `library.d.ts`. In case there are multiple versions supported, the latest one will be without a version number in the file name. Older versions will be in the form of `library-1.0.d.ts`.

I think we need to rename `node.d.ts` file to `node-0.8.8.d.ts` and create a new file named `node.d.ts` to node 0.10. I don't know all differences between node 0.8.8 and 0.10.1, but, we can verify it and update to new `node.d.ts` file.