Update Aug 27, 2019: Minor change in how equations are solved (from version 0.9.0.9122).
We (Søren Højsgaard and I) are preparing a new major release of Ryacas (GitHub). It will have a new interface to yacas that is thinner, cleaner and more robust. It relies on yacas’s RForm() function rather than an OpenMath XML interface.
It also means that the API has changed in Ryacas: new functions are introduced and old ones deprecated.