This is the core libsrs2 against which you should be linking your MTA. Please submit patches to srs [ta] anarres.org.
Check the code out from github:
If your distribution isn't listed, or the package is out of date, please contribute a new package. The developers might not have access to a system running your distribution.
Several other people have written elements of SRS implementations. This is by no means a comprehensive list, and the libsrs2 developers are not responsible for these projects, nor can the compliance of these projects be guaranteed (but is stated where known). Some of these contributions are finding their way into the libsrs2 development stream, and it is hoped that more will follow.