I'm not new in unix's, but anyway every platform has its own issues in development and porting.

As i'm also now interested in porting some apps to maemo5 on n900, and also newbie(only week with this phone). I want to point you (by the way xfoil is also interesting for me ).

So you definitely should read:
http://wiki.maemo.org/Documentation/...K_Installation

SDK installation process is trivial if you installing on Debian system.

And then, i think you need to read:
http://wiki.maemo.org/Port_an_existing_Debian_package

then go to the debian xfoil page:
http://packages.debian.org/squeeze/xfoil

here we can see that(AFAIK) we have only problem with libgfortran3 package. Its unavailable in maemo repos.

I tried to install both packages in a straight way and despite dependency errors, xfoil started and seems to work. Maybe its enough to you for work, but i must to say better will be if you try to port them to maemo.

And because it works that way, i think it will not be super hard task.

P.S. I think second way will be install easy-debian package and work with xfoil in chroot.