I have to admit I am still trying to understand that statement. In the interview you found with Dr. Ari Jaaksi [18], at around 9:55 he said that most of the work will come out if a developer wants to adapt the "Linux application" to the Maemo 5 UI. Is that what : "Debian ARM packages can be used if they are modified with the maemo-optify tool for example" means ? I am far from being an expert with Linux so I was just wondering.

Linux is the kernel but typically also happen to refer to all the tools that compose a full system. The GUI API in Maemo is a bit different and adapted to a tablet screen. Thus, normal Xorg application might look ugly and not conform to certain rules used in the Maemo window manager which may cause them to be not very practical to use.

I believe he was referring to reprogramming graphical elements to fit in with the platform more fluidly. If you don't care about modifying the GUI the porting process is supposed to be trivial. maemo-optify just moves all the files larger than 2KB into the /opt directory and puts symlinks where they were originally. This has to be done because of the uniqueness of the file structure of maemo 5 and the limited space available in /. The complexity of application compatibility is quite large in embedded linux and I just feel it's misleading to claim that it is Linux and will run Linux applications when there are a lot of qualifiers. Perhaps someone with embedded coding experience can offer some insight into what is and is not possible in porting applications especially in regards to the GUI.