[alexvoda]

They can do that regardless of the license since they own the copyright. As long as they do not accept external contributions or require a CLA it does not matter what license they offer, they can still make future versions proprietary.

[Matumio]

Even if they accept contributions normally (e.g. under the same license), the above licences will allow them (or anyone else) to make a proprietary fork.

[jhasse]

True, that's why there needs to be a distinction between "GPL" and "GPL with CLA".

[zer0tonin]

> they do not accept external contributions

They do tho.