There's an open-source project that I'm interested in and use regularly. It's licensed under the Apache License 2.0 and it has basically no activity any more. It's hosted on Google Code and I'm interested in continuing it's development. I'm new to the open-source process and I'm trying to figure out the appropriate way to go about this. Can I just check it out and push it to github so I can continue it's development in the open there? Should I contact the project "owner" first? Also, do I leave all the author information at the top of the classes, etc even though I'm going to be making changes..(I'm assuming the answer is yes)?

Also, how do I practically adhere to the license requirement of "all modifications are clearly marked as being the work of the modifier"? Do I place a comment by every change I make?