I took a look at
PLS web site and didn't get the impression that it's open-source. Quite the contrary. You can download binaries (after registration) but license states that "no dissasembly or reverse engineering allowed". The source code download states, that:
"The PLWeb Turbo 3.0 source code distribution allows you to rebuild the application-level binaries of PLWeb Turbo 3.0. The libraries that are part of the search engine (CPL) are provided as binaries in the CPL 6.3 binary distribution and cannot be rebuilt (i.e., no source code is provided)."
In summary: it's not an open-source software and nothing seems that it'll ever be.
