[cctalk] APL-11 sources

I was just wandering through some old disk images and spotted something I missed for years: a directory holding what looks like a set of source files and build scripts for APL-11. I have no idea where this came from or why I have it; while I have used APL I have not used it on a PDP-11, nor ever installed it. Is this something others already have that is a known to be good version, or should I go dig through this and verify it, then archive it properly? paul