Starting with V0.80, XFolder has been placed under the GNU General Public Licence (GPL).

The GPL is a general licence agreement which was developed by the Free Software Foundation to protect the rights of programmers who wish to publish the source code of their software. The GPL is most frequently used with software of the GNU project and has become more widely known with the evolution of Linux, to most parts of which the GPL applies.

If you're interested in finding out more about OpenSource licencing models and why I think that all OS/2 freeware developers should release their source codes, preferrably under some OpenSource licence, please read my article in OS/2 e-Zine!, vol. 4, no. 4 (http://www.os2ezine.com/v4n4/open.htm).

More readings can be found here:

"The Cathedral and the Bazaar"
  by Eric S. Raymond. Probably one of the most influential Internet articles ever written. This is what convinced Netscape to release the Mozilla sources.
"The Bazaar and the Other Bazaar" and "GNU's Not Linux"
  by Chris Wright, both of which can be found in OS/2 e-Zine! vol. 4 no. 1 (www.os2ezine.com/v4n1/).
www.opensource.org,
  the new Web center for OpenSource information and advocacy. This site also has the "Halloween documents", commented by Eric S. Raymond. I strongly recommend reading this.
"OS/2 Headquarters"
  by Tom Nadeau. This has the "Learning from Linux" series, another commented version of the "Halloween documents" with focus on OS/2.
GNU's Not Unix!
  Homepage of the GNU Project and the Free Software Foundation, with lots of articles.