In any case, as I understand it the GPL does not allow you to distribute it's software without passing on the rights granted by the GPL to others - in other words, giving access to the source code. How do you plan on doing this? I'm not exactly a FOSS expert, so I've not read about how others do this.
Because of the GPL, the sources or changes of the ported applications should be made available to the public. Since SkyOS is not actually released yet, you will not find them yet, but they should be available on request.
As this only concerns the applications, there is no obligation to open the source of SkyOS itself. (just like windows is not open source, while running OSS)
edit: this would be different if the kernel contained GPL code, which not the case.