I just read Dunn's 1979 paper Relevant Robinson's Arithmetic, and the end especially caught my interest. Following the surprising role of constant functions in collapsing "relevant Q with zero" to classical Q but leaving "relevant Q without zero" nontrivial, Dunn writes:
[T]he idea of functions that really depend on their arguments has been articulated and investigated recently by many. [...] A typical motive in such investigations has been to do for relevant logic what Lauchli did for intuitionistic logic, namely to provide a "realizability" interpretation [...] the relevant trick being to look at only those functions that depend on their arguments. [...] What is needed is a "relevant Kleene," developing a theory of "relevant partial recursive functions" that really depend on their arguments, and using these to investigate "relevant realizability interpretations" of the relevant arithmetics. ([...] It is not the case that "representability in ${\bf Q_R(1)}$" coincides with "relevant recursiveness" (perhaps what is needed is some notion of "relevant representability").)
Basically, Dunn suggests three intertwined topics - relevant realizability, relevant recursiveness, and relevant representability - which sound quite interesting to me but unfortunately go well beyond my background. My question is whether there has been any work since Dunn's paper on these topics.