Since FPM isn't around any more, you can't get legal new copies of PSL. Somebody might be selling used genuine copies; in general that should be OK, but check the CD - some (mine included) are not top-quality and sometimes will throw errors when installing. If somebody's making copies of the old CDs, that's not OK.

Not sure who would enforce it, but the trainsim.com forum did post a copy of the FPM license which everybody who actually got a copy is bound by - it's a pretty standard (we own everything; you just get to use it) software license. Since t...sim.com posted it prominently and has occasionally removed things that look like they're infringing, I suspect there is a lawyer watching.

If all you're interested in is the equipment (F59PHIs, cars, etc. - quite good models really) you can get those from the original developer, 3DTrains I think. Frankly, except for the trackwork and a few stations the route was never much better than beta quality despite being sold for a substantial sum; you might be better off with the freeware version that has been done since then.