Commercial Plugins and Solo Licensing? Brand new Craft user.  Second day playing with it, and so far, loving it!

I believe the Solo license allows a Freelancer to roll off personal (for her own use) implementations for free -- even if those sites have a commercial purpose.

I understand this to mean I may power more than one site for free under the terms of the Solo license.

Question: Does this Solo licence freedom extend to paid plugins?  

For example, I want to purchase the commercial Enupal Backup plugin.  I would like to use it on my two Solo-licensed Craft websites.  Can I do it, or must I purchase the plugin twice?
Technically, that's up to each individual plugin developer. But realistically, the vast majority of commercial plugins are only valid for a single site.

If it's a paid plugin, you'll probably need to pay for it on each site independently.


  "I may power more than one site for free under the terms of the Solo license."


It's important to realize that you're actually working with multiple licenses in this case... they just all happen to be Solo (aka free). Each site has its own license, you are not sharing a Solo license across multiple sites.