1) Regarding plugin licenses, for a WordPress multisite installation do we only need to purchase one site licence or are we required to purchase a licence for each site in the network, and does this differ should a plugin require registration after installation or does the WordPress system just see this as one installation of the plugin.
**As far as Plugin licenses goes, each plugin developer licenses their plugin differently. For e.g Listify Core theme is 100% GPL on ThemeForest.
Screenshot below.

According to GPL license, you can resell anything that’s under that license.

Now it seems weird morally to generate income on someone else work, hence my encouragement to work with the plugin authors, Even if there is a percentage of recurring income going to plugin authors to keep helping them support the very plugin that generating you income.
So it all depends on your communication with the dev authors and understanding GPL license
More on GPL license here https://www.gnu.org/licenses/gpl.html#section6
2) If the client wishes to have one of our multisites customised slightly with maybe an extra plugin or a different setup let’s say in the case of a booking site, the client needs some extra fields, or in the case of a company logo, how does this affect the platform in general, such as when an update is released for a plugin which we may have modified for this client etc.
Because WordPress Multisite is similar in architecture to a basic SAAS platform, It’s easy to customize aspects of the Site e.g styling, specifications, behavior etc. Customisations are also depended and constiolled by the core Plugin you are selling. e.g Woocommerce Booking Plugin can be customised on Client level since Woocommerce controls the Feilds etc, So yes you can make individual specification changes. If the changes and customisation are not possible from ready-made plugins, then this is something that needs to be custom built. Thankfully there is a neverending supply of WordPress Developers.
3) I see the last video is not up yet and I assume your still working on your own site and will produce the video as you go along, any idea when we will be able to follow along with the testing of the site installation etc.
I have already made some tests, Will be doing the final video shortly
4) I’m looking forward to your release of some of the plugin’s you mention on your sales page such as your own booking plugin, could you update us on the progress.
Absolutely, We are working on few things here now
1) Auto Deployment of SAAS platforms
2) Marketplace with Plugins that you can use to built SAAS platforms.
We are still a month away on this, I will keep you all updated.