Google has acquired San Francisco-based AppJet in a move that's thought to be in order to bolster its Google Wave offering.

AppJet offers "EtherPad", a kind of Google Docs rival that gives its users the ability to upload documents and collaborate on them in a real-time, online basis.  

"We are happy to announce that AppJet Inc. has been acquired by Google. The EtherPad team will continue its work on realtime collaboration by joining the Google Wave team", AppJet says in a blog post.

The EtherPad site will stay online until March 2010, and due to an outcry by users unhappy about the news, will be obtaining Wave invites for all EtherPad users to try out the service.

"We do realize (as does the Google Wave team) that Wave doesn't yet have all the functionality you rely on, and isn't yet as mature as EtherPad", AppJet says.

"We are confident that in the long term you will be really happy with Google Wave, though. That's why we decided to join them!"