There exist open source steam functions at least (Score 1)

This would be easy for steam properties. XSteam: http://www.x-eng.com/Download_XSteam.htm They explicitly state that their functions are open source, substantiated by the fact... you can download the code real easy right there. I've been using their Excel visual basic code. No, they don't have any for Fortran, but their VBA stuff is not hard to figure out, and I've actually been able to change the code and use it in Fortran. It's not that different. If you desperately need free Fortran steam tables, I wouldn't even have a problem sharing what I have. As for the steam tables themselves, XSteam claims to use IAPWS IF97, which seems pretty thoroughly public domain. They have other options available on http://www.iapws.org/ as well. ...But now for Hydrocarbon Mixtures, I'm not sure what to tell you. A lot of people here are talking about the formulation of the tables constituting significant intellectual work, and that's true, but there is public domain government work and open source solutions for steam tables, and considering that the data for hydrocarbon stuff is also clearly public domain, I don't know. I'm just as lost as you are.