Proftpd is reported to compile and function on the following platforms,
Linux 2.0.x & 2.2.x (glibc 2.x only), 2.4.x BSDI 3.1 & 4.0 IRIX 6.2, 6.3, 6.4, 6.5 Solaris 2.5.1, 2.6 & 2.7, 8, 9 AIX 3.2, 4.2, 4.3.3 OpenBSD 2.2/2.3 FreeBSD 2.2.7, 3.x, 4.x, 5.0 Digital UNIX 4.0A, 5.1A, 5.1B DEC OFS/1 UnixWare 7 SCO OpenServer 5.0.5
Some platforms require that compilation is done with gcc (or one of it's variants) while other platforms only function properly if compiled with the compiler shipped with the OS. Experiences vary and at this time there is no reliable list of which platform requires what.
Only the essential core modules are compiled in by default, most of the more interesting features such as sql support, upload/download ratios etc etc are contained within the non-standard modules.
Including additional modules is only possible at compile time, at the moment there is no chance of dynamically loadable modules entering the 1.2.x code tree. This is primarily due to time and the need for some major structural changes within the code to support dynamically loadable modules.