I want to use a webpage as a texture. How do I do it?

And is a pro licence required as it is for MovieTexture?

Well, there's quite a few possible ways to do this. One is rendering the Webpage to an image on a Web server and then downloading that image in your game and displaying it. For that, the Pro Version is not required and it would also work with Web players. However, you need a Web server where you can do this, and you need to implement rendering the Web page into an image. For this, see for example Render HTML as an Image (there's a few solutions provided in the different answers so don't get discouraged by the first answer which doesn't have any info on that). Also, it will probably be quite tricky to implement interacting with the page - so it's "look, don't touch". Finally, flash or javascript on the page will most likely be ignored.

For an approach directly integrated into Unity, see bliprob's htmlTexture plugin. For that, however, you will need the Pro license - and as far as I know, as it's based on WebKit and Cocoa, this will only work on the Mac. However, bliprob is considering doing a Windows port for pay.