In one of his articles on finishing, Russ Fairfield discussions Waterlox, and then goes on to describe a finish that he made by blending equal quantities of an alkyd spar varnish, pure tung oil, and turpentine. While he never actually said that his blend was equivalent to Waterlox, that was the implication that I took away from the article. I have been using using ever since, and I like it a lot.
That said, I have not used it on pens for the simple reason that its pretty time consuming - wipe it on, let it soak in for up to an hour, wipe it off, let it cure for a few hours, denib with a gray scuffie, and repeat at least two more times. It does buff nicely although its not going to yield a really high gloss.
I've used ordinary wipe-on poly (both solvent and water based) on pens and my experience is that it holds up very well. But my preference remains a lacquer-based friction policy (equal quantities of a brushing lacquer, lacquer thinner and either BLO, Tung Oil or Walnut oil). It goes on quickly, cures rapidly, can build to a high finish that can be either buffed to a gloss, or wiped with a gray scuffie for a satin finish, and holds up well with use.