CPL is a free license, that's why it was accepted on Savannah. However
it is true that you cannot combine CPL 1.0 and GPL v2. It looks like
this issue is more or less debated, maybe you could send some
encouragements to the Eclipse and SWT people to update their licensing
scheme to something GPL compatible, it would benefit everybody.
From here, you can either choose another toolkit (like GTK+), or
relicense your project (CPL or BSD comes to mind). You'll have to
contact us again to change the displayed licensed on your project page
when you have made up your mind.