documentation for forwarder licenses is here:
http://docs.splunk.com/Documentation/Splunk/5.0/Admin/TypesofSplunklicenses#Forwarder_license
the tl;ldr answer is: no. if you're installing a universal forwarder, it will not be indexing any data, so you don't need to install a separate license on it (it comes with its own separate license pre-installed and enabled).
the universal forwarder is a separate package and should be installed as needed on the system(s) from which you want to forward data. review this topic and others about forwarding:
http://docs.splunk.com/Documentation/Splunk/latest/Deploy/Aboutforwardingandreceivingdata
if you are going to be indexing data on that forwarder, you do not need a separate license, but you will need to add it as a slave to your license master and give it access to the enterprise license stack per the docs link i provided above.
i'm planning on installing heavy fowarder as we need the indexing feature of the heavy indexer.
do i need another liecense in this case?