<p>I'm coming from the open source world, and interested in giving ASP.NET a spin. But I'm having a little trouble separating the tools from the platform itself in regards to the licensing. I've downloaded Visual Web Developer 2008 Express, but not sure how different this is from one of the full-featured Visual Studio licenses -- and whether or not my Express license will prevent me from using all the features of ASP.NET.</p>

<p>Is a Visual Studio license just an IDE, or does it include pieces of .NET not available to the Express license?  What about the other tools like IIS and SQL Server?</p>

<p>Thanks.</p>

All of .net is available in the .net SDK, so in theory you will not need Visual Studio at all.
Now, there are some things that Express will not do. For example, the Database Designer is not very comprehensive and adding different remote databases is not or only very hardly possible. Still, in code you can connect to everything.
There is also no Remote Debugger, no support for creating Setup Files (well, that does not apply to ASP.net anyway), no real Publish Web Site Feature (although that can be
added manually
as it's just a Frontend for a SDK tool), no integrated Unit testing (and Microsoft
loves to threaten people
who add it), etc.
For a full comparison, see here:
Visual Studio 2008 Editions
But as said: Functionality of .net is all in the SDK, Visual Studio is just making it a bit easier to work with.