Yeah, looks like it is. It says "GNU General Public License version 2.0 (GPLv2)", and the project page describes it as an open source project. I thought it would be good etiquette to check first though. For example, I wouldn't want people to think that the github repo was the new official place for the code, unless Dr Zoltan was happy with that. So maybe I can describe it as a "fork" of the sourceforge project.
Interesting point about GPL that relates to github. I think that by putting your code in to a free github account, you are agreeing to this: " "By setting your repositories to be viewed publicly, you agree to allow others to view and fork your repositories". Apparently it doesn't require your project to meet the definition of open source, but you do need to agree to that bit in quotes. If you want to use a particular type of open source license, then you are advised to put it in a file called LICENSE or something like that. So I guess I add such a file with the GPLv2 license in it.