No, you do not need any special license for this. Trunking might be a good idea if there is a lot of traffic between the switches. You could group multiple Inter-Switch Links (ISLs) into a single logical trunk and the switches will then automatically load-balance across all ports in a trunk. But for that you need Trunking Licenses on both switches that are connected to each other. You already have it on switch2, but it would depend if you have the license on the other switches, too.