The main requirement is performance (a missing point in your list). If Git would be a good candidate as a versioning system for DCC software packages, it would have been picked up by now, but it didn't happen, among others because of the reasons listed above. Git addresses a completely different target audience and lifecycle than SnowFS. The commit hash integrity is a problem in CG/VFX productions, so is the 4GB limitation, as well as the I/O performance for large binary files. The fact that these issues are still there are fully understandable, given the responsibility and dependencies of this project. That's why SnowFS tries to address the niche requirements with its light implementation.
In terms of the license, this is intentionally the weakest argument of all. It doesn't prevent anyone under the GPL to ship Git as an external program with a commercial software, same counts for libgit2 with its linking exception. So there is not even a real benefit here. But the chosen MIT license is an open invitation for everyone.
P.S. Certain features and technical solutions will be feature-proposed to libgit2