All chrome extensions can be copied and installed locally...Assuming the source code doesn't protect against something like this. You could take this extension,

All chrome extensions can be copied and installed locally...Assuming the source code doesn't protect against something like this. You could take this extension, copy the obfuscated source, then load it locally to avoid auto updating in the future. Chrome generally doesn't like apps that load their bg page scripts via web requests to help increase security. So it's likely that they aren't doing this.