GnGeo vs NeoCD/PS2

GnGeo is a free NeoGeo emulator for Linux, with the project also describing possible support for other Unix systems. It runs NeoGeo ROM sets identified by their MAME names; the listed example starts Metal Slug with `gngeo mslug`. Command-line options include home, arcade, and unibios modes, as well as fullscreen display, scaling, interpolation, raster interrupts, blitters, and visual effects. Sound and joystick support, player controls, and hotkeys are configurable. Settings can be supplied on the command line or in user and per-game configuration files. The project describes graphical frontends with features such as game previews and configuration options. GnGeo requires SDL 1.2.x, libz, and a NeoGeo BIOS; NASM 0.98 is optional for i386 assembly optimization. Games must be ZIP files, while the BIOS must not be, and the default search location is `$prefix/share/gngeo/`. The README describes a source build using `./configure`, `make`, and `make install`. The repository lists no releases, and its licensing notes forbid commercial use of GnGeo as a whole because of included code and licensing.

NeoCD/PS2 is a free, open-source NeoGeo CD emulator for the Sony PlayStation 2. It is a port of NeoCD/SDL, adapted to replace SDL components with PS2-native libraries using PS2SDK. Games load directly from the CD-ROM. Video offers PAL/NTSC auto-detection and selection, while the in-game menu includes filtering, fullscreen video, and frameskip controls. The emulator supports two controllers, stereo sound emulation, and CDDA playback. NeoGeo CD memory card support uses 45 KB on a PS2 memory card. ZIP support is limited to the BIOS, and the NeoGeo CD BIOS is not included; users must find it or dump it from their own system. The releases page lists version 0.6c with CDDA fixes, including an auto-loop feature. Listed issues include sound problems when the frame rate is below full speed, timing issues, graphics glitches in some games, and needing to reset the PS2 to exit the BIOS. The project is distributed under GNU General Public License version 2 and says use is at the user's own risk; the README says it should only be used with games the user legally owns.