Source code licensing, forks, relicensing and copyrights

Hi, everybody!

I have few uncertainties on how to proceed with source code licensing and copyright notices.

What I did was, to take a look at somebody's MIT licensed code, took the basic idea and wrote my own version of it. Well, probably I also copy-pasted a few lines and then modified them to suit my project's structure. To some degree I consider my code a derivative of his work. Now I'm intending to publish it (incidentally also under MIT license). However, I'm slightly unsure how to proceed with license’s condition:

The above copyright notice and this permission notice shall be included in all copies or substantial portions of the Software.

(In this case) keeping a permission is not a problem, since my intended license is the same. But what about "The above copyright notice"? Should I keep his line:

Copyright (c) 2012 Original Author author@email.com

and append my (c) alongside?

To broaden the problem, what to do if I want to reuse portions of BSD licensed code? And what if something is under GPL (not sure how RasPi patches for Linux kernel are licensed)?

I do not want to appear to be "stealing" anything, I really appreciate what other coders are doing. But I'm intending to collect a library of bare-metal samples how to use RasPi hardware. And, of course, I'd like to keep my library somewhat consistent.

Should I keep his line:

Copyright (c) 2012 Original Author author@email.com

and append my (c) alongside?

IANAL, but I suggest: "Copyright 2012 Original Author author@email.com" followed by "Modifications Copyright 2012 Velko velco@email.com" on the next line or separated by a semicolon. The "(c)" designation is not a valid substitute for the Copyright symbol ©. Ether use © or the word "Copyright".

For details on USA copyright, see http://www.copyright.gov/circs/ circular 3 (Copyright Notice) and circular 14 (Copyright Registration for Derivative Works).

From MIT licence:

The above copyright notice and this permission notice shall be included in
all copies or substantial portions of the Software.

I would guess that 'substantial portions' means more than odd snippets or lines of code. This is very open to interpretation though! I would not have a problem if people look at and use my MIT code for inspiration. Keep the licence and copyright if you are re-using a whole file's worth of code though.

The MIT licence is not copyleft unlike the GPL licence. You can take MIT code and relicence it under a new licence. GPL code and any modifications have to remain under the GPL licence forever and can't be converted to MIT unless you are copyright holder for all the code.

By the way, IANAL but tend to use the MIT licence for any code I write. I am far from an expert on software licences though!