Sure, but at the same time if it's not included on distributions and not updated by upstream it's likely to have compatibility issues relatively quickly (GTK is particularly bad at maintaining compatibility between versions, even point releases).
Also code not being updated is something, TLS certificate not being renewed is in an other league in terms of lack of support of the project.
Also code not being updated is something, TLS certificate not being renewed is in an other league in terms of lack of support of the project.