I have this issue with licensing. I downloaded a third-party class from GitHub and it's under the GPL v3 license. However, I used this class on another open-source project which is under the GPL v2 license, and submitting my script there, requires that everything is under GPL v2 from my side too.Am I allowed to change the license for that class, even though I am not the author?
Downgrading from GPL v3 to GPL v2
licensing;gpl
From the Free Software Fundation:When we say that GPLv2 and GPLv3 are incompatible, it means there is  no legal way to combine code under GPLv2 with code under GPLv3 in a  single program. This is because both GPLv2 and GPLv3 are copyleft  licenses: each of them says, If you include code under this license  in a larger program, the larger program must be under this license  too. There is no way to make them compatible. We could add a  GPLv2-compatibility clause to GPLv3, but it wouldn't do the job,  because GPLv2 would need a similar clause.There is no way you can use GPLv2 and GPLv3 code in the same program and/or upgrade the licence.