Don't have the information at hand, but I seem to remember posting it in a previous thread.
The current (and as mentioned above it is under review) requirements for a TV licence are based on the equipment to receive the signal (hence the problems that were raised for mobile home owners a short time back) of which a Television set is the obvious one. A computer may be able to recieve the information over the net, but suggesting that all computers are used for watching TV is obviously untrue.
Currently I can't see any TV licence inspector pulling anyone for viewing live streams on a PC, but simply as the legislation has not kept pace with the technology (how many people were streaming live TV a decade ago?).