ocfs2 is not a fork of ext3 and neither is ocfs2-tools a fork of e2fsprogs. But both have benefited a _lot_ from ext3. In some instances, we copied code (non-indexed dir layout). In some instances, we used a different approach because of collective experience (indexed dir). grep ext3 fs/ocfs2/* for more.
The toolset has a lot more similarities to e2fsprogs. It was modeled after it because it is well designed and to also allow admins to quickly learn it. The tools even use the same parameter names where possible. grep -r e2fsprogs * for more.
BTW, ocfs2 has had bigalloc (aka clusters) since day 1, inline-data since 2.6.24 and metadata checksums since 2.6.29. Yes, it does not have delayed allocations.