R calling other programs in the server

I will install RStudio program in R. The R program calls other open source programs. These will also be installed in the server. Since I am using the single threaded version of R, and the open source programs are called from the R program, these open source programs will be called serially as the R program is. I wonder if there could be some concurrent use of the open source programs. I do not know if these are single threaded or multi threaded for concurrent user requests. (I should find that out). Is there any thing that I should keep in mind that might have a negative effect in the R program is other users run the open source programs from their PCs while an R program is calling an open source program?

How will this be deployed in the shiny server?