It depends on what you're doing with that source. If it's for reference, yes, that's a good place.
/usr/local is reserved for software installed locally by the sysadmin. So, if you want to install software along with source files (for other programs to use or for people to look at), that's good.
It's not meant, however, to be a workspace. Since it is local, you can do whatever you want, of course, but this isn't designed to be the place to put your software development tree.
That should, really, be in a code repository (possibly in
/srv/sourcerepo or something), and then developers would check out their own working copies into their home directories.