Re: Sorry, but why do we need so many Open Source licenses ?
Why there is quite so very many licenses is hard to answer briefly but the major cleft among FOSS licenses is between two approaches. The distinction comes down to quite who is granted the most freedom:
- with "copyleft" licenses the emphasis is on the end-user, ensuring that they are _always_ passed the four freedoms;
- with "permissive" licenses, the emphasis is on other developers/programmers, including allowing them to _not_ pass on the four freedoms.
What you see happening with cases like Redis, is changes of mind about which of those types suits their business practice. Whoever creates code gets to choose a license, and it would seem pointless to not allow people to change their mind as they go along. Bearing in mind that generally, any code already published with a license embedded will retain that license as long as valid copies exist somewhere.