Yes, you can freely use it, that’s why it is opensource.
You can modify your deployment the way you want, my recommendation is to stick as possible to the upstream so you can easily update.
This depends on the type of deployment, will you be using one machine where jicofo and jvb will be running. Will you deploy multiple jvb machines. Depends on the available bandwidth for jvb.
This also depends on the type of deployment, will it be one shard (one web and one jicofo with one or more jvbs), for example, at the moment meet.jit.si runs in 6 geo locations with at least 2 jvb per location, they autoscale based on the bandwidth.
yes u can use it commercially for free completely!!
yes u can use your own company logo
in short unlimited. but the number of videos u see is subject to how you configure your jitsi-meet instance and video quality depends on your client and server side bandwidth and CPU strength.
in short unlimited. it all depends on number of bridges u are hosting and their individual cpu power and bandwidth. for example, in my company we host 1 jitsi-meet server with 3 additional bridges all in AWS we can do about 20 concurrent meetings where by each meeting has atleast 3-5 participants and so on.
If you are interested my company can help you setup a robust server. you can contact us at email@example.com