After reading the post Why is Wolfram Language free to use, but Mathematica is not? I wondered about the appropriateness of implementing a subset of the Wolfram Language in another language like Julia.

Background

I first saw Mathematica in action while speaking with Stephen Wolfram in 1986 regarding tetration and fractional iteration. In 1992 I bought my first copy of Mathematica and have used it on and off for thirty years. Several years ago I reconnected with Stephen Wolfram and he provided me a copy of Mathematica on a year by year basis. Last year I submitted my FractionalIteration function to the Wolfram Function Repository. I also posted here about the Mathematica license and professional grade neural networks where I expressed questions and concerns about what my Mathematica license allowed me to do.

Currently

Due to being unable to resolve my licensing concerns I no longer use Mathematica. I would need the professional version in order to publish the results of my research on my website. I'm retired and don't have several thousand dollars to spend. What I do have is time and programming ability. So I have moved to Julia and Jupyter notebooks. But I need a bit of functionality that Mathematica provides in order to implement my fractional iteration software in Julia. Using Mathematica's RSolve function allows me to express my work tersely. Plus having a rules based engine would be nice addition for Julia. So what are the relevant issues to implementing the Wolfram Language in another language?