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Calendrical Calculations and licensing

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Dave Rolsky
January 15, 2003 12:44
Calendrical Calculations and licensing
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I just got my copy of Calendrical Calculations but I'm afraid to read it.

The license in the book is _extremely_ restrictive, saying:

  The Functions (code, formulas, and calendar data) contained in this
  book were written by Edward M. Reingold and Nachum Dershowitz (the
  "Authors"), who retain all rights to them except as granted in the
  License and subject to warranty and liability limitations below.
  These Functions are subject to the books copyright.

Then it says "The Authors' public service intent is more than liberal
than suggested by the License below ...", and goes on to explicitly
mention web sites and academic usage.  However, no mention is made of
Free Software style distribution of source code.

The license in the book reads:

  LICENSE: The Authors grant you a license for personal use only.  This
  means that for strictly personal use you may copy and use the code and
  keep a backup or archival copy also.  Any other uses, including
  without limitation, allowing the code or its output to be accessed,
  used, or available to others, are not permitted.

This is _really_, _really_ bad.  Not only are they explicitly limiting use
of the code in the book, they are also limiting use of the _algorithms_.
Frankly, that is f*cked up.  Imagine if the Perl Cookbook from ORA had a
similar license?  What the hell would be the point of buying it?  You
wouldn't be able to use any of the algorithms (much less the code itself)
in any software your wrote, Free or not!  How about if Donald Knuth did
the same thing?

Because of this, I think we need to take the following steps:

1. No implementation should explicitly use algorithms from CC.

2. No discussion of implementation matters should refer to Calendrical
Calculations.  For example, don't tell someone else "go read chapter X".
Because if they read chapter X and then implement it, they can't
distribute it.

I'd guess that we can use algorithms from Claus Tondering's FAQ, but it'd
be best to get an explicit statement to that effect from him first.  The
copyright on his pages only says "The document may be freely distributed,
provided this copyright notice is included and no money is charged for the
document."  No mention of the algorithms it contains.  But absent an
explicit license grant we have no rights.  I will contact him to clarify

Rich, I know you have talked to the CC authors before, and were going to
email them about licensing.  I think this is a _huge_ issue, and if you're
on friendly terms with them perhaps you can talk to them about this.
Honestly, I don't know what the heck they were thinking.  What's the point
of a book with algorithms that you can't use?

What makes this even weirder is that Reingold wrote (and still maintains,
I think) calendaring code for Emacs!


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