Default fonts for platform, theme & logo

Background

The topic of default fonts has come up again (raised by Roy as he is trying to organise promotional materials for SlideWiki). When I put together the colour options for the logo I made the following observations:

• Default font for Semantic UI components is Lato, used on this slides & for “WIKI” in the logo
  • Sitka Text has been used for “Slide”... this is a Microsoft font and there is no clear license information on restrictions on its use 
• This is reasonably clear, but certain letters may be more difficult for some to read – a g e
• An alternative Open font is OpenSans which may also be quicker to load and support more characters set http://www.allbloggertricks.com/2014/04/open-sans-vs-lato-comparison.html
• Other open fonts: https://www.smashingmagazine.com/2014/03/taking-a-second-look-at-free-fonts/

I have also noticed that the default font in the slides is Helvetica (based on Reveal theme) and this can sometimes be unclear

Free Serif fonts available in Latin, Greek and Crillic scripts -  Font Squirrel Serif - NB its not so important to have a Serif font supporting other scripts as currently we only use it in the logo.

Free Sans Serif fonts avaible in Latin, Greek and Crillic scripts -  Font Squirrel Sans Serif

Here are some versions of the logos with similar fonts. The top one is the existing combination.

Unresolved items

• Are we happy to have closed fonts in the logo or do we want to find an alternative to Stika? 
• Are we happy to keep Lato in the logo and as the default font for the platform?
• Do we want the default slide theme to match these fonts or to use more familiar fonts?