Hi,

I haven't used invision for a while now and I'm planning to renew my licence. I want to use the forum and the blog. I was wondering if it is possible to set the blog as the homepage?

Yes. You can set any application as the default one. 

Randy is correct.

And to set Blog specifically, click the hollow "star" icon to the right of the Blog application entry on the ACP -> Applications page. The star should turn solid, which indicates it's now the default app.