An IRC Bot in Arm Assembler

The SFLC had a chance to set this straight in the aftermath of the inflammatory 2007 episode around the Atheros driver. Instead they dodged the entire relicensing question and released a set of guidelines which focus on where and how to preserve the copyright notice, and that rather seems to only have reinforced the idea that the permissive BSD style licenses are nothing more than a decorative text you must lug around. So we still have a huge number of people who think they can do anything (e.g. "relicense") as long as the decoration is kept in place. It really is a shame.

So when you place a license on your work, you are just granting people these rights which would normally be exclusive to you as the owner, granted to her by copyright. Again: copyright is not one of these exclusive rights, copyright is property the author owns. When people receive a copy, they do not receive ownership or copyright.[2] They receive a physical copy of a work but the "intellectual property" is still held by the author. At no point was it transferred. And you cannot on your own claim and transfer the author's ownership of the property any more than you can take his home or car or wife. What you can do (as the license permits) is to practice these rights such as copying, performance, etc. which are normally exclusive to the owner.

Re-assigning or transferring copyright (in the sense that you become the owner and can sue the original author as Alupis intended) quite literally means transferring one's property to someone else. If the author of a work transfers his copyright, he no longer owns the work. It gets a new owner, just like your car would do if you gave it to someone else. Transfer of copyright is not at all the same as granting other people the same rights you have. In the US, such exclusive transfer of copyright cannot happen without black-on-white and the signature of the owner:

[1]

Any or all of the copyright owner’s exclusive rights or any subdivision of those rights may be transferred, but the trans­fer of exclusive rights is not valid unless that transfer is in writing and signed by the owner of the rights conveyed or such owner’s duly authorized agent.

[2]

Mere ownership of a book, manuscript, painting, or any other copy or phonorecord does not give the possessor the copyright. The law provides that transfer of ownership of any material object that embodies a protected work does not of itself convey any rights in the copyright.

[1][2] http://www.copyright.gov/circs/circ01.pdf

EDIT: Furthermore, under the Berne Convention, original authors have the moral right to be known as the author. This right is inalienable: you can't give it away, and it cannot be taken away; you have that right even after everything else (i.e. the economic rights) is exclusively transferred to someone else. I think that makes Alupis' idea of claiming someone's code as his own work illegal.

So, in short, no, you can't re-assign copyright to yourself and then sue the original author for copyright infringement. No, you cannot claim to be the original author and to own the work. No, you do not become the owner of the work when you receive a copy along with a license that allows you to further copy, modify, distribute, perform, etc.