They just wanted the CLA to support the (paid) relicensing.
I think the reasoning (as it was explained to me) was that when people made their original contributions, they were agreeing to the license at that time (in this case GPL, but for other projects MIT). But the other contributors never agreed that the main maintainer could relicense their contributions for a fee.
The upshot was that we went with an in-house fully-proprietary alternative. More expensive, probably lower quality.
I think the reasoning (as it was explained to me) was that when people made their original contributions, they were agreeing to the license at that time (in this case GPL, but for other projects MIT). But the other contributors never agreed that the main maintainer could relicense their contributions for a fee.
The upshot was that we went with an in-house fully-proprietary alternative. More expensive, probably lower quality.