We are using this openAM 9.5 RC1 branch source in our project. https://github.com/svn2github/openam.git
In order to fix some bugs, we have to modify existing openAM's amserver library. For this, we have downloaded the source code from above location and tried to compile it offline using ant (as stated in README). But we are not able to compile it anyhow (even after making necessary changes, adding dependencies etc.)
Is there any way to construct required library (amserver.jar) from this source code ?
The OpenAM 9.5.x and 10.0.x versions are rather difficult to build, but from 11.0.0 the build process should be much more simpler since the project has been migrated over to Maven build system. In any case, the version you are using (Snapshot 9.5.1 RC1) is very much outdated and most likely has several critical issues (not to mention the security issues).
I would strongly advise against putting effort into backporting fixes to that ancient version. Instead you should realize that you are running a more than 4 years old version of a security component, and upgrade your system to a more recent version as soon as possible.