Is it valid to include binary or categorical variables in redundancy analysis (RDA)?

Question

I have a mix of continuous and categorical explanatory variables I would like to enter into a canonical redundancy analysis (RDA), but I'm not sure whether it is valid to use discontinuous variables in this type of analysis? My question stems partly from the fact that discontinuous variables aren't suitable for PCA and other associated techniques, and the structure of RDA is partly like a PCA.