I've created my first font typeface as a side project. I want to release it for free, for both personal and commercial use. It will just be advertised on my website and on twitter for people to download. Do I need to include a license with it? How do I obtain one? I keep reading about OFL license, Creative Commons but I'm a bit confused.
Check how others do - generally there's always a license file included which declares who was the creator and what is allowed and required. In addition the font file itself contains copyright notices. If you skip it you can get a bill where you are ordered to pay because you have distributed a font which is owned by someone else. That someone had caught a freely drifting treasure and done the paperwork to benefit himself.
When you put a font on your web site and say:
Everybody is free to use this font for every purpose.
you already are providing license, albeit a minimalistic one: The blockquoted text is the license; you are licensing people to do with your font whatever they want. This is not a disaster, but there are some advantages to use an existing license intended for such purposes instead, such as the OFL:
These licenses are crafted by expert for people exactly like you, so you and users of your font do not have to worry about legal details and cannot get into legal pitfalls.
There are ways to use or abuse your font that you may not even have thought about. For example, you may not want somebody to sell your font under some disgusting name. Good font licenses prevent such things, and only such things.
Using such a license makes it much easier for others to distribute your font, for example by including it in a Unix distribution, font collection, etc., to the extent that your self-made license may the one reason that prevents it. People who manage such collections do not want to read and particularly interpret your custom license, even if it is only one sentence. They want to see a license they already know and have checked to be compatible with what they are doing.
Also see: How can a “crayon” license be a problem?
Therefore I recommend to read the OFL (it’s not that long and complicated). If it sounds reasonable to you, use it. Otherwise have a look at other font licenses.
Also note that most, if not all font formats allow you to include the license as meta information in a dedicated place within the font itself. This is a good idea since it prevents the license getting separated from the font itself.