Copying this SoftwareXrtti is copyrighted by its author, Bryan Ischo, and released under the GNU General Public License Version 2. This means that you may not redistribute this software in source or binary form unless you adhere to the terms of the GPLv2. The full text of the GPLv2 can be found here.
Why the GPL?You might wonder why this software is released under a GPL license. It is because the GPL guarantees the freedom of all end-users of Xrtti to modify it to suit their needs and to re-distribute it under the same terms.
An alternative would be to release it under the BSD license or to the public domain with no copyright whatsoever. However, this would allow someone else to create software based on Xrtti and distribute it to users without access to the source code. If I am going to release the source code to anybody, I would prefer to release it to everybody, and the GPL guarantees this in ways that the BSD or public domain do not.
Another alternative would be to release the software in binary form only with no source code. This would guarantee a monopoly on changes to the software to myself, the author. But it would prevent end-users from modifying the software to suit themselves, and would prevent people from submitting improvements to the software back to me.
And, just because the software is released under the terms of the GPL doesn't mean that I can't issue a separate release under different terms to anyone willing to pay for the privilege.
I see the world of software development split into two camps: those who give their software away for free, for everyone to use, recognizing the benefits that everyone enjoy when everyone shares. And then there are those who sell software in binary-only form, for the purpose of profiting for their work. I personally have no issue with either approach, and am happy to contribute back to the free software world that has given me so much great software. But at the same time, I have no problem if my code is used in a proprietary software package also, as long as I get paid for it!