Why did you download an old version from the forums when Altera ships a
newer version with the NIOS-II EDS? They are supporting Interniche as
'primary' TCP/IP stack, but lwIP is still shipped for 'legacy' projects
(or at least with the last version I checked last year).
I think I remember this software being free for private usage and
available at www.altera.com.
I have their Cyclone III 8.1 NEEK development kit and it had nothing lwIP
related in it except for an Ethernet driver for the lan91c111 in files: