Yeah, they accept patches at their forum
http://neosource.1emulation.com. They have a repo but private (for known contributors.) Alternatively, pm dink on there.
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Some information about the current state of rerecording in FBA (and what would be needed to add to make it a viable TASing emulator in order):
* Deterministic replays. This is the biggest issue: currently replays will only start recording from a savestate. After asking, recording from power on (without savestates) was disabled because it caused crashes.
There is an incredibly hacky workaround for this (but it works!): load the game, then click outside the FBA window (anywhere on the desktop, from example.) After this, the game will be paused: from there, select Game > Record input and record your movie as normal.
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Frame advance Implemented, press F1 - bindable to other keys.
* Read only & Read+Write functions - not implemented.
* Ability to bind savestates to multiple slots - currently you can only bind them to one slot, and have a separate hotkey to switch slots.
The file format used is the same one as in blip's rerecording builds (fr).
I've made a page about it.
For the rest, the implementation is solid in general (it doens't shit itself on Neo Geo, for example, and syncs properly on CPS1/2/3) and FBA has support for more games, such as, for example, Neo Geo CDs.