Post#3 » Wed May 23, 2018 8:44 pm
To give a slightly more in-depth reply...
KallistiOS is the most widely-used homebrew development library/SDK for the Dreamcast. Basically, it is a collection of code that helps you interface with the hardware of the system in a fairly coherent manner. It also provides several nice abstractions to make development easier and more PC-like (such as hooks for many standard C library functions, a TCP/UDP IPv4 and IPv6 stack with BSD-compatible (ish) sockets, and several add-on libraries that have been ported to it). Basically, it's something that programmers can use to make games/applications/etc for the Dreamcast. Yes, it's possible to use it to help in porting stuff from a PC, but it doesn't do that for you -- there's still an awful lot of work in most cases to make something work with KallistiOS that wasn't necessarily designed for it.
I'm the current maintainer of KallistiOS, although I'm not the original author.