[jitendrac]

Yes you can, if owner(All owners with code contributions) gives you full ownership explicitly. Find contributors section on open-source projects like mysql, they only accepts pull accepts with dual licensing. also, you can use WTFPL. You get it, you own it.

[kube-system]

The OP says they have:

> signed an assignments clause

Only the entity with a copyright to a work can license it.

If that assignment clause is valid for this work, then whoever they assigned it to (i.e. their employer) has the right to license it.