ical.net is a fork of Douglas Day's dday.ical library for .NET 2.0 as it appeared on SourceForge. This is why you may see references to dday throughout the code. I contacted Doug, and was able to get his permission to re-license it. Per his wishes, I chose the most permissive license I could: the MIT license, which you will find in license.md.
The old license--recorded below for historical purposes--has been superceded by the MIT license.
This is a copy-and-paste of our email exchange.
From: Rian Stockbower
To: Douglas Day
Date: Mon, May 2, 2016 at 7:04 PM
Subject: dday.ical
Hi Doug,
Are you the original author of dday.ical? If so, I've been looking for your
contact info--and mostly coming up empty--so I could ask you some questions...
So first off, there's a github repository that's a mirror of the old sf svn
repo, but the person maintaining that mirror doesn't own the copyright (nor
does he claim to):
https://github.com/mdavid/DDay.iCal/blob/master/License.txt
I have a number of performance enhancements that I've made to the library, and
I'd like your permission to create an open-source, Apache-licensed fork called
ical.net, free to world. But doing that isn't compatible with your copyright
notice.
I was wondering if I could have your permission to use dday.ical as the basis
for that Apache-licensed ical.net that could live its own independent life?
I'd prefer to have this conversation over email, but ddaysoftware.com domain
doesn't seem to go anywhere anymore.
Regards,
-Rian
From: Douglas Day
To: rstockbower@gmail.com
Date: Tue, May 3, 2016 at 11:07 AM
Subject: RE: dday.ical
Rian,
You found me! Thanks for getting a hold of me--indeed, that project is dead,
and I have no time to contribute to it anymore. It makes me very happy you
are interested in moving it forward, as it was a passion of mine for many
years.
Please consider this e-mail full permission to fork and relicense the library
--my only request is that its new license remain as free and open as the
original license (it appears you want this as well). My copyright claims were
more meant for self-protection rather than to protect intellectual property, so
you also have my permission to put a different copyright notice or eliminate
the copyright notice altogether, if preferred. I want the project to be as
open-source as possible.
Also, please let me know the final resting place of the source, as it would be
nice to be listed as a contributor (and may contribute now and again if I can).
Also, my usual e-mail address is <snipped>. Feel free to contact me there with
anything else.
Regards,
Doug
For posterity, here is the original license, now void. It has been superceded by the MIT license found in license.md.
The DDay.iCal library, its documentation, and its source code
are Copyright © 2007 Douglas Day <doug@ddaysoftware.com>.
All rights reserved.
Redistribution and use in source and binary forms, with or
without modification, are permitted provided that the following
conditions are met:
* Redistributions of source code must retain the above
copyright notice, this list of conditions and the
following disclaimer.
* Redistributions in binary form must reproduce the above
copyright notice, this list of conditions and the
following disclaimer in the documentation and/or other
materials provided with the distribution.
* Neither the name "DDay.iCal" nor the names of
its contributors may be used to endorse or promote
products derived from this software without specific
prior written permission.
THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND
CONTRIBUTORS "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES,
INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF
MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT OWNER OR
CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES;
LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR
OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE,
EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.