Nimbus is part of dev.globus
To gain committer status and rights to the git repository, you need to be accepted into the project (via voting) and join the dev.globus community.
You can still contribute without this voting process and many do. All that is necessary is that you sign a contributor's license which allows us to freely distribute your contributions. Your git author information is preserved in the repository, you just don't have free reign in this situation.
Nimbus used to be known as "Virtual Workspaces" or the "Workspace Service" (which is just one Nimbus component). This is why the dev.globus Virtual Workspaces page is named like that.
"Virtual Workspaces is an effort undergoing incubation at Globus. Incubation is required of all newly accepted projects until a further review indicates that the infrastructure, communications, and decision making process have stabilized in a manner consistent with other successful Globus projects. While incubation status is not necessarily a reflection of the completeness or stability of the code, it does indicate that the project has yet to be fully endorsed by Globus."