The only difference between planning an Open Source project and planning not to go Open Source is that in an Open Source project anyone has the ability to review the code, 'own' the code, use the code, and *gasp* evaluate the projects source. If you don't have an Open Source project, you can hide your code, only let those whom contractually bind you audit your product, and produce binaries that are specific to one OS and platform.
Also; just because it is Open Source it doesn't mean that it will be a Linux/GNU project (but one can hope). If it is on WinNT/Solaris/BeOS/HPUX/etc.. then you should still aspire to use Open Source.
I know I want all government funded software that has no reason not to be released, freely available and accessible by the real government - the people, you and me.