The [SWS extension](SWSExtension) is on [github](https://github.com/reaper-oss/sws).
Also there is the  [REAPER SDK](https://github.com/justinfrankel/reaper-sdk).


See this [forum thread](https://forum.cockos.com/showthread.php?t=225736).

[Julian Sader's extensions](https://github.com/juliansader/ReaExtensions)