You can install shiny directly from github using the devtools package. In order to install shiny you'll also need to be configured to build R packages from source. To install devtools and verify that you can build packages from source:
install.packages("devtools")
library(devtools)
has_devel()
If the has_devel function produces an error then you'll need to install some additional components required to build packages from source:
Next, you need to install a modified version of the websockets package from github:
install_github("R-websockets", "jcheng5")
Finally, you can install the shiny package from github:
install_github("shiny", "rstudio")
To verify that Shiny is installed correctly you can run an example application:
library(shiny)
runExample("01_hello")
If everything is installed and working correctly a browser will open and navigate to the running application.