ProjectCenter and Linux
ProjectCenter is running on any system which has support for GNUstep. While there are some issues on non x86 platforms related to Objective-C and GNUstep, there are no reasons why ProjectCenter should not run on any other GNUstep aware system.
Why port to just Linux?
If GNUStep is to be what it wants to be, let's not focus on Linux (or any other single OS). Let's make sure it's all very very portable so that everyone can enjoy it!
I realize that it in this context the author may have equated Linux with GNUStep platforms, but let's just be sure that we maintain portability!
An open, cross-platform journaling program.
A scientific plotting package.