I got MSTR SDK from my friend who installed MSTR in his laptop. Inside the SDK I do have CustomizationPlugins, DevelopmentKits, lib, samples and tools folders.
My question is with out actually installing MSTR in my system can I run the SDK using eclipse for web customization?
If you work on MicroStrategy Web SDK customizations when you setup the MicroStrategy Plugin for Eclipse you have to set the MicroStrategy Web Folder: the changes you will make will be saved in that folder.
To have MicroStrategy Web on your machine, it's enough to copy and unpack the MicroStrategy war file from a MicroStrategy installation (so you need at least to install MicroStrategy somewhere, but you don't need to install it on your machine)
Using Eclipse I assume you are working on the MicroStrategy Web JSP and that you have a Tomcat server installed on your local machine.
If the MicroStrategy Web folder used by the Eclipse plugin is one of the Tomcat webapp you can test easily it on your machine.