You can get the source distribution of the current (and other) version of LibRCPS from the links below. Please have a look at the changelog to find out if the newest version includes any improvements relevant to you.
If you want to use cutting-edge versions of LibRCPS, which are of course not guaranteed to do anything useful, you can access the source tree with SVN (ignore any issues with the certificate for now):
svn co https://www.librcps.org/svn/librcps librcps
You can then later update your copy by entering the directory and issuing a
Should you have problems using SVN or need a client, please visit the SVN homepage.