I don't think that's quite right - Rebble has updated a number of these apps to keep them supported. As sibling commenter posted, the original apps are available publicly.
Updated themselves? Or accepted/hosted updates from third parties?
Updated themselves
Are they still open source? If so, why does it matter who updated them?
I think that’s the crux of the issue is rebble isn’t under any obligation distribute them open source, unless say the original app had a “copyleft” policy?
AFAIK the original apps were individually licensed by the creators... so Rebble would need to have permission before claiming anything for their own except in the case of explicit permissive licenses (like MIT). In some cases (copyleft licenses) Rebble would be required to make their maintenance also open source.