Restrictions in license

Brian Behlendorf brian at
Sun Sep 25 18:44:58 UTC 2005

On Sat, 24 Sep 2005, Russell Nelson wrote:
> Joerg Friedrich writes:
> > Yes, for example there would be a clause limiting the number of concurrent
> > sessions on a web server.
> An Open Source license cannot restrict use.  You would need to form a
> contract to do that, and while you can encourage the recipients of
> your software to execute a contract, you cannot require them to.

Sure.  But they could (by copyright law) state that you have no rights to 
redistribute a modified version that changes that limit.  So you can 
modify that software yourself to remove the limit, but you can't pass that 
modification on to someone else.  One wonders whether changing a 
hard-coded limit into one that can be changed as a matter of run-time 
configuration could be redistributed.

It looks like rule #3 might address this, but it's hard to tell.  Such 
a license would certainly "allow modifications", just not all possible 
ones.  Should #3 have read "allow ALL modifications"?

I think such a license would be abhorrant, but we need a better answer as 
to why it's not allowed by the OSD.  Are there any existing certified 
licenses that changing #3 to "allow ALL modifications" would affect?


P.S. - why doesn't the qmail license qualify as an Open Source license 
given clause #4?  That license restricts my ability to distribute qmail in 
modified form - but doesn't prevent me from distributing patches.  The 
license "explicitly permit"s distributing builds, see the bottom of:

but these derived works have to behave exactly the same.  So what kind of 
license was #4 designed to allow?

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