TheXSoft.com is the home of of a free software, that 100% free it does not suddenly turn into shareware,bundleware,beggingware.

Because windows requires administrative rights write to the default folder to install applications in Radio Stream Player installer will require administrative rights to be installed. It will NOT require administrative rights after being installed.
You can get around this requirement in 2 ways:

1) Dont download the installer but rather the zip file, and extract it where you want and run it from there ( Recommended ) 
2) Dont install in the default application folder, but in some other folder where you have write access.