I can answer a couple of your questions. It sounds like you’re looking for the opinions of other community members, so I’ll start with the disclaimer that I’m a developer at Couchbase, but I work on the SDK team – not on Couchbase Server. This is my view from the bottom
- Can we continue to use 6.x using the old licensing terms.
Yes, absolutely. Anyone may continue to use Community Edition 6.6 and earlier under the old license terms. Reference: Couchbase Modifies License of Free Community Edition Package
- If there are critical bugs, we would like to fix them on 6.x branch and contribute back to community. Is this allowed.
Couchbase Server is open source, and contributions from the community are welcome. However, according to the documentation on the Community Edition (CE) vs Enterprise Edition (EE):
The release version of CE is several months behind EE. CE also does not include the latest bug fixes.
Reference: Couchbase Server Editions | Couchbase Docs
Historically, it’s unusual for Couchbase to release more than one or two patch versions for each minor release of CE (which has been a contentious issue in itself).
@ingenthr might have a better perspective on this.