Hello!
On Sun, Sep 16, 2007 at 05:12:08PM -0400, Theodore Tso wrote:

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>[...]

>What is going on whenever someone changes a code is that they make a

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>"derivative work".

Only if the additions/changes are significant enough to be copyrightable

on their own.
>Whether or not you can even make a derivative

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>work, and under what terms the derivitive work can be licensed, is

>strictly up to the license of the original.  For example, the BSD

>license says:

>  Redistribution and use in source and binary forms, with or without

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>  modification, are permitted provided that the following conditions

>  are met....

>Note the "with or without modification".  This is what allows people

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>to change BSD licensed code and redistribute said changes.  The

>conditions specified by the BSD license do not mention anything about

>licening terms --- just that if you meet these three conditions, you

>are allowed to redistribute them.  So for example, this is what allows

>Network Appliances to take BSD code, change it, and add a restrictive,

>proprietary copyright.

Right. You may add nearly any copyright *on your own significant

additions/changes*. However, BSD/ISC explicitly requires to retain the

BSD/ISC terms, too (applicable to the original part of the combined

work).
>So for code which is single-licensed under a BSD license, someone can

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>create a new derived work, and redistribute it under a more

>restrictive license --- either one as restrictive as NetApp's (where

>no one is allowed to get binary unless they are a NetApp customer, or

>source only after signing an NDA), or a GPL license.  It is not a

>relicencing, per se, since the original version of the file is still

>available under the original copyright; it is only the derived work

>which is under the more restrictive copyright.   

No. The derivative work altogether has a *mixed* license. BSD/ISC for

the parts that are original, the other (restrictive, GPL, whatever)

license for the modifications/additions.
*If* you choose to distribute source along with the binaries, the part

of the source that's original is BSD/ISC licensed even in the derivative

work (though one may put *the additions/modifications* under restrictive

conditions, e.g. of commercial non-disclosure type source licensing).
>[... dual-licensing issues etc. already handled in other mails ...]
Kind regards,
Hannah.