I'm going to take a few moments to try and explain this new license and
the reasons behind it in plain English.  The legalese for the license can
be found online at http://creativecommons.org/licenses/by-nc-sa/2.0/legalcode
and should be read and understood in detail before you use this code.

This new license was chosen because of a failing with the GPL.  It only
covered distribution of source if and only if binaries were distributed.

In a web environment, specifically an interpreted web environment, merely
installing a game does not constitute distribution, and therefore people
were taking our work, making modifications to it and not releasing the
source code to their modifications so that the entire community could
benefit.  They worked with the letter but not the spirit of the law.

Investigation on the part of the authors however, led to the fact that the
right of public performance was one of the rights normally restricted to
copyright holders, AND that computer programs, specifically video games and
interactive ones such as Legend of the Green Dragon were considered to be
publically performed if run from a public server.

The new license restricts public performance of the work unless the source
code of the modified work is made available on demand.

In plain English, this means that if you put this game on a web server and
allow people 'outside of a normal circle of family and its social
acquaintances' to play there, then you are publically performing this work and
MUST either a) make any and ALL changes which you make to the game available
on request (note this doesn't have to be available via the online source
display link, but they must be able to ask you for the code AND receive it
in toto), b) make arrangements privately with the authors wherein they
grant you a special license, or c) remove the code entirely from the machine.

We do recognize that people want to have areas of their game which are theirs
and theirs alone.  To that end we will make the following exception to the
normal requirements for source code distribution -- any module file which is
not modified or derived from a module file included in the base distribution
AND which does not require any other module files AND which does not require
any modifications to the core code (code distributed with the base release)
may be withheld at the authors discretion.

For purposes of this license, base releases of this code include all versions
created and distributed by Eric Stevens and JT Traub.  In addition to these
versions, the developers at Dragonprime.net are hereby granted a revokable
authority to produce new distributions which enjoy the same restrictions and
exceptions as this entire license.  This authority may be revoked at any time,
but such revocation will be purely proactive, and existing releases will still
enjoy the full liberty of this license. 
Although revocation may be for any reason, the only foreseeable reason that such
revocation would be enacted is if these distributions were discovered to contain
module hooks designed to circumvent the spirit of this license. The intention is
to let these developers continue where Eric and JT have left off.

We also want to make very clear that version 0.9.7 (also known as version
0.9.7+jt) was the final version released under the GPL.  All versions,
starting with the 0.9.8-prerelease code are only licensed under the Creative
Commons license.  We EXPLICITLY deny the right to import any code from a
0.9.8-prerelease or later release into a 0.9.7 and earlier release.  Allowing
this would cause that imported code to be released under the GPL and that is
not something we wish to allow.  Authors of modifications to 0.9.7 will
need to re-release their modifications as derivitives/modifications to
0.9.8 code and place them under the same Creative Commons license. It must
be done by the original author since only the original author has the right
to change the copyright or license upon their work.  [Additionally,
reworking the modifications will be a good idea anyway as the mechanism for
making modifications is substantially cleaner/clearer starting with the
0.9.8-prerelease code.]