What’s the deal with CLAs? I’m not familiar with them.
To avoid this situation, some projects require their contributors to sign contributor license agreement. Terms might differ, but generally you allow your contribution to be relicensed in any way in the future. So today Matrix's AGPL, tomorrow they can go proprietary and you're OK with that. Also they want to sell their source code with proprietary license (so buyer's not obliged to open his modifications) and they also need contributor permission to do that.
Basically it's a commercial project which is not interested with external contributions.
That depends on the CLA's wording. A CLA could allow the right to sell commercial licenses to the code while always keeping the same code under the AGPLv3.
I haven't read Element's CLA though.
That would be impossible toddeploy to app stores like the Apple App Store because that store is inherently incompatible with (A)GPL. The only way you can publish (A)GPL code to iPhones and iPads legally is to dual license all code from all contributors.
With a CLA, a project can relicense the code to itself. Without it, the project can't upload their own project to the App Store and similar platforms.
I think you'd be crazy to run Synapse on a phone, but Dendrite is built to be much more efficient for such use cases.
I would never sign an open-ended CLA, though. For all I know, the project (with my code in it) could end up being bought by Oracle, proprietized, and used by Larry Ellison to construct the Torment Nexus.
[0] https://en.wikipedia.org/wiki/Contributor_License_Agreement#...
That would be meaningless - they could relicense it to MIT, distribute that MIT-licensed version to their subsidiary, and then have that subsidiary sell it under whatever proprietary license they wanted.
It is only required if you intend to move to an open-core model, or intend to eventually make the project non-open-source entirely. This is a common first step for many organisations that have moved in this direction.
The announcement even makes it clear that they intend to ship versions for a fee, so it's very likely that we'll see a "community edition" and a "full edition" at some point. Or some other model which amounts to the same general idea.