Craft CMS solo licence It mentions developers can use it for personal usage. Does that include commercial usage as well? It seems so, but am not sure. 

I have a few small personal sideprojects running with some Adsense and Affiliate links (currently on CodeIgniter, etc.).
According to Pixel &amp; Tonic:

Can I use Craft Solo for client work?
Technically yes, however, we don’t recommend it. Craft Solo is meant to be a solution for developers to get to know Craft and create one-off sites for themselves and their friends. We do not recommend giving admin access to non-developers and therefore strongly recommend that any professional work is done on Craft Pro. This ensures the best experience for everyone.

So as long as you're ok with everyone having admin access (and no branding and no developer support), it's fine, including for commercial usage.