On the Strategy Download Site, there is an option to download the Strategy Runtime Environment 8 separate from the rest of the products. This Strategy Runtime Environment is different from the Java Runtime Environment, and is used for customizations with SDK.
The Strategy Runtime Environment is a collection of core libraries and configurations necessary to run any SDK solution. Attempting to install the Strategy Runtime Environment when components of Strategy already exist will result in the following error:

Setup has detected that some Strategy products are already installed on the machine. You cannot install the Strategy 8 API Runtime on a machine where other Strategy products are installed.
You will need to remove all Strategy products from the machine before you install the Strategy 8 API Runtime.
Setup will now terminate.
This is because the Strategy Runtime Environment is a set of common files which has conflicts with the regular installation of Strategy. To prevent these conflicts, the Strategy Runtime is blocked from proceeding rather than resolving these conflicts.
The Strategy Runtime Environment is similar to the Strategy SDK. Users can attain a license key from their Account Executives and install Strategy SDK, in addition to the other products. However, if users do not want to install any other product, they can just install the Strategy Runtime Environment using the SDK license, which will install the libraries, .jar files, DLLs, and other files, and use the Runtime as their SDK.
An enhancement has been logged to include documentation on Strategy Runtime Environment in the product manuals.